book one
of the zoological group Carnivora.
The Laboratory of Comparative Pathology at this Garden speaks for the earnest desire on the part of the Directors to use the material to its fullest extent, and I, acting for myself and my associates, wish to record our appreciation of the facilities offered to us for study, and for the broad-minded, scientific coöperation the Board has always displayed. The President, Charles B. Penrose, M.D., Ph.D., LL.D., was the active originator of the plan whereby this department was started, and he has given to it continuously the support of his rich experience. I wish to express for myself the deepest appreciation of his personal interest in my studies, and assistance which has been constructive and stimulating. Whether or not this present work prove useful to the extent that is hoped, the results from the Laboratory are such as to make the scientific world debtor to this gentleman.
It is a duty, and a pleasant one, to record, though unfortunately in memoriam, my association with Arthur Erwin Brown, A.M., Sc.D., Ph.D., C.M.L.Z.S., for many years the Secretary of the Society and Executive Officer of the Garden. Doctor Brown as teacher was ever ready to help in the broad subject of biology, and I am proud to recall that he guided me also as a friend.
The first director of the Laboratory was Courtland Y. White, A.M., M.D., who served from 1901 to 1906, retiring then to accept a position in the City Laboratory. The foundation of the recording system is still in use essentially unchanged from his plan, and is a credit to his foresight. Our clerk and technician, Miss Harriet M. Phelps, has served the Garden faithfully and well since 1906. The condition of the museum is very much due to her interest and watchfulness. Thanks and appreciation for her work are felt by every one, the author most of all. Dr. F. D. Weidman has been our first assistant since 1911, and his work on parasitology has been of the greatest value, practically and scientifically. It is to be hoped that we shall be able to retain him indefinitely. Dr. E. P. Corson-White has in recent years taken an assistant position with us, armed for the work with a thorough knowledge of applied organic chemistry and immunology, and has already obtained useful results.
ZOOLOGICAL CLASSIFICATION │
MAMMALIA
PLACENTALIA
PRIMATES
_Simiadæ_ Anthropoid apes
_Cercopithecidæ_ Old World monkeys (macaques, baboons).
_Cebidæ_ New World monkeys (capuchins, howlers, spiders).
_Hapalidæ_ New World monkeys (marmosets).
LEMURES
_Lemuridæ_ Lemurs, Loris, Galagos.
CARNIVORA
_Felidæ_ Cats
_Viverridæ_ Civets, Genets, Paradoxures, Ichneumons.
_Hyænidæ_ Hyena.
_Canidæ_ Dogs, Wolves, Foxes, Jackalls, Etc.
_Mustelidæ_ Marten, Skunk, Weasel, Otter, Badger, Etc.
_Procyonidæ_ Raccoon, Bassaris, Coati, Kinkajou.
_Ursidæ_ Bear.
_Otariidæ_ Eared Seal, Sea Lion.│These are grouped │separately as suborder, │PINNIPEDIA, illustrating │water carnivores.
_Phocidæ_ Common Seal, Walrus. │ „
INSECTIVORA
_Tenrecidæ_ Tenrec.
_Solenodontidæ_ Solenodon.
_Talpidæ_ Moles, Shrews.
_Erinaceidæ_ Hedgehog.
CHIROPTERA
_Pteropodidæ_ Fruit Bats, “flying foxes.”
_Vespertilionidæ_ Common bats.
_Emballonuridæ_ Snouty Bats, Free-tailed Bats.
RODENTIA
_Sciuridæ_ Squirrels, Spermophiles, Marmots.
_Castoridæ_ Beaver.
_Muridæ_ Rats, Mice.
_Geomyidæ_ Pouched Rats, “Gophers.”
_Dipodidæ_ Jumping Mice, Jerboas.
_Heteromyidæ_ Kangaroo Rats.
_Octodontidæ_ Capromys, Coypu.
_Hystricidæ_ Porcupines.
_Chinchillidæ_ Viscacha, Chinchilla.
_Dasyproctidæ_ Agouti, Spotted Cavy.
_Caviidæ_ Guinea-pig, Capybara.
_Leporidæ_ Rabbits, Hare.
PROBOSCIDEA Elephant.
HYDRACOIDEA Cape Hyrax.
UNGULATA
PERISSODACTYLA (odd toed)
_Rhinocerotidæ_ Rhinoceros.
_Tapiridæ_ Tapir.
_Equidæ_ Horse, Ass.
ARTIODACTYLA (even toed)
_Bovidæ_ Oxen, Antelopes, Sheep, Goats.
_Cervidæ_ Deer, Moose, Elk.
_Antilocapridæ_ Prong-horned Antelope.
_Giraffidæ_ Giraffe.
_Tragulidæ_ Chevrotains, Muis Deer.
_Camelidæ_ Camels, Llama.
_Hippopotamidæ_ Hippopotamus.
_Suidæ_ Swine, Warthogs.
_Tayassuidæ_ Peccaries.
SIRENIA Sea-cow, Manatee, Durong.
CETACEA Whales, Porpoises.
EDENTATA
_Bradypodidæ_ Sloths.
_Dasypodidæ_ Armadillo.
_Myrmecophagidæ_ Anteaters.
MARSUPIALIA
MARSUPIALIA
_Didelphyidæ_ Opossums.
_Dasyuridæ_ Dasyures, Tasmanian “Devils.”
_Peramelidæ_ Bandicoots.
_Phascolomyidæ_ Wombat.
_Phalangeridæ_ Phalangers.
_Macropodidæ_ Kangaroo, Wallabies.
MONOTREMATA
MONOTREMATA
_Echidnidæ_ Echidna, Ornithorhynchus.
AVES
PASSERES
_Turdidæ_ Thrushes, Robins, Etc.
_Sylviidæ_ Warblers, Kinglets.
_Paridæ_ Titmouse.
_Troglodytidæ_ Wrens, Mockingbirds, Catbird, Etc.
_Pycnonotidæ_ Bulbul.
_Crateropodidæ_ Babblers, Jay-thrushes.
_Oriolidæ_ Oriole.
_Motacillidæ_ Wagtails.
_Dicruridæ_ Drongos.
_Mniotiltidæ_ Chats, Warblers, “Woodwarblers,” Etc.
_Cœrebidæ_ Sugarbirds.
_Vireonidæ_ Vireos.
_Laniidæ_ Shrikes.
_Ampelidæ_ Waxwing.
_Hirundinidæ_ Martins, Swallows.
_Meliphagidæ_ Honeyeaters.
_Tanagridæ_ Tanagers.
_Ploceidæ_ Weavers, Whydah birds, Waxbills, Finches, Etc.
_Fringillidæ_ Finches, Sparrows, Buntings, Grosbeaks, Etc.
_Icteridæ_ Hangnests, Troupials, Grackles, “Blackbird,” Etc.
_Sturnidæ_ Starlings, Mynahs.
_Corvidæ_ Crows, Jays, Magpies, Jackdaws.
_Alaudidæ_ Larks.
_Tyrannidæ_ Tyrans.
_Cotingidæ_ Bellbird, Cock-of-the-rock, Etc.
PICARIÆ
_Upupæ_ Hoopæ.
_Trochilidæ_ Hummingbirds.
_Cypselidæ_ Swifts, “Chimney Swallow.”
_Caprimulgidæ_ Night hawk, Whip-poor-will.
_Coraciidæ_ Roller.
HALCYONES
_Alcedinidæ_ Kingfisher.
_Momotidæ_ Motmots.
BUCEROTES
_Bucerotidæ_ Hornbill.
TROGONES
_Trogonidæ_ Trogons.
SCANSORES
_Picidæ_ Woodpeckers.
_Rhamphastidæ_ Toucans.
_Capitonidæ_ Barbets.
COCCYGES
_Cuculidæ_ Cuckoos.
_Musophagidæ_ Touracous.
PSITTACI
_Loriidæ_ Lories, Lorikeets.
_Cacatuidæ_ Cockatoos.
_Psittacidæ_ Macaws, Conures, Amazons, Parrots, Parrakeets.
STRIGES
_Strigidæ_ Barn owl.
_Bubonidæ_ All other owls.
ACCIPITRES
_Falconidæ_ Buzzards, Hawks, Falcons, Eagles, Etc.
_Serpentaridæ_ Secretary Vulture.
_Catharidæ_ Vultures.
COLUMBÆ
_Treronidæ_ Fruit pigeons.
_Columbidæ_ All other pigeons and doves.
PTEROCLETES
_Pteroclidæ_ Sand grouse.
GALLI
_Tetraonidæ_ Grouse, Ptarmigans.
_Phasianidæ_ Pheasants, Fowls, Turkeys, Quail, Etc.
_Cracidæ_ Curassows, Guans, Etc.
_Megapodidæ_ Brush turkey.
HEMIPODII
_Turnicidæ_ Hemipodes.
FULICARIÆ
_Rallidæ_ Rails, Porphyrios, Gallinules, Coots, Etc.
ALECTORIDES
_Aramidæ_ Courlan.
_Eurypygidæ_ Sun bittern.
_Gruidæ_ Cranes.
_Cariamidæ_ Cariama “Crane.”
_Psophiidæ_ Trumpeters.
LIMICOLÆ
_œdicnomidæ_ Thicknees.
_Charadriidæ_ Plovers, Sandpipers, Curlews, Woodcocks, Etc.
_Chionidæ_ Sheathbills.
GAVIÆ
_Lariidæ_ Gulls, Terns.
_Stercorariidæ_ Jaeger Gull.
PYGOPODES
_Colymbidæ_ Loons, Grebs.
_Alcidæ_ Auks, Murrs, Puffins.
IMPENNES
_Spheniscidæ_ Penguins.
STEGANOPODES
_Sulidæ_ Gannets.
_Pelicanidæ_ Pelicans.
_Phalacrocoracidæ_ Cormorants.
_Anhingidæ_ Darter “Water turkeys.”
TUBINARES
_Procellariidæ_ Petrels, Fulmars.
HERODIONES
_Ardeidæ_ Herons, Bitterns, Egrets.
_Ciconiidæ_ Storks, Ibises.
_Plataleiidæ_ Spoonbills.
ODONTOGLOSSÆ
_Phœnicopteridæ_ Flamingoes.
PALAMEDEÆ
_Palamedeidæ_ Screamers.
ANSERES
_Anatidæ_ Swans, Geese, Ducks.
STRUTHIONES
_Apterygidæ_ Kiwis, Apteryx.
_Casuariidæ_ Cassowaries.
_Struthionidæ_ Ostriches.
_Rheidæ_ Rheas.
CRYPTURI
_Tinamidæ_ Tinamous.
_List of Animals subjected to Autopsy giving the number of each. These Figures are used to obtain the percentages quoted in the Tables and Text._
MAMMALIA Primates 498 Lemures 86 Carnivora 481 Pinnipedia 20 Insectivora 6 Chiroptera 5 Rodentia 198 Ungulata 365 Proboscidea 3 Hyracoidea 7 Edentata 16 Marsupialia 175 Monotremata 0 1860 ————
AVES Passeres 1355 Picariæ 87 Striges 133 Psittaci 689 Accipitres 196 Columbæ 157 Pterocletes 0 Galli 299 Hemipodii 2 Fulicariæ 35 Alectorides 37 Limicolæ 6 Gaviæ 20 Pygopodes 0 Impennes 5 Steganopodes 21 Tubinares 0 Herodiones 98 Odontoglossæ 6 Palamedes 5 Anseres 317 Struthiones 32 Crypturi 5 3505 ———— ———— 5365
SECTION II DISEASES OF THE HEART
The heart is an organ whose duty, throughout the two classes considered in this study, remains entirely identic, purely a physical one in driving the blood through the corresponding vascular system. The physics involved naturally differs between mammals and birds, but energy is derived from the automatic power lodged in the cardiac musculature. Whether this be neuromyogenic, as seems to be the case in all mammals, or purely myogenic, as is probably the case for the birds in which MacKenzie and Robertson[5] say there is no atrioventricular bundle, the result is the same, since in both classes there is some continuity of muscle fibres from auricle to ventricle. The gross anatomy varies little if any more than the physiology, albeit there is proportionately greater auricular capacity in the mammals than in the birds, and indeed there are differences within the classes which cannot now be readily explained; certain minor variations of valvular arrangement exist, such as the absence of the membranous light tricuspid in Aves.
When, however, one considers the cardiac power available for various animals, the subject becomes one of greater breadth and complexity, for no consistency obtains even within families, since the demand for cardiac strength will vary more with habits than with zoological relationships. Thus for example the domestic rabbit has a small heart volume while the wild hare has a great one. Although, of course, the size of an organ may not be an absolute measure of its efficiency (a flea’s leg muscle has relatively greater power than a man’s), yet size is the only physical gauge one has for estimating nature’s preparation for expected demand. Perhaps this will be shown later when after discussing the pathological anatomy of the heart in the wild mammals and birds, we can study these changes in light of statistics upon the relative size of the heart.
EXPRESSION OF CARDIAC DISEASE.
The diseases of this organ are known only by their physical effects, chiefly by causing physical or functional defects in other organs and to a minor degree by purely physiological irregularities in the heart itself (tachycardia, arrhythmia). All the latter and most of the former are subjects discovered by observation during life and unfortunately cannot be included in the study at hand. Both states are well known to the veterinarian who diagnoses them with reasonable ease in animals that can be handled; I saw one case of arrhythmia in a monkey for which no adequate gross morbid explanation was found postmortem. Some of these functional abnormalities are certainly caused by myocardial disease and cardiac failure has occurred among many orders. An interesting observation was made by Plimmer[6] on several large birds (ostriches, storks, cassowaries) which apparently died from this condition; at autopsy he found myocardial degeneration, or epicardial edema or only a flabby heart. Lack of exercise was held responsible by this observer. Such cardiac deaths have probably been encountered at this Garden but we have accounted them to shock, or gastrointestinal disease; this matter will be discussed on a later page.
CORONARY ARTERY DISEASE.
If a degenerative sclerosis of coronary vessels be the cause of angina pectoris then perhaps paroxysms of this kind occur, for we have seen such anatomical changes in the heart of three widely separated varieties of animals, a Nylghaie, a Hamadryas Baboon, a Macaque, and a Brown Pelican. The history of these animals does not register anything resembling the clinical picture of angina pectoris in man, and they did not come to their death from the arterial changes in the heart alone since sufficient other pathology also existed.
KINDS OF PATHOLOGICAL CHANGE.
As an introduction to the strict pathology of the heart it might be well to outline the headings of the scheme upon which it seems desirable to study the subject. It is hardly profitable to take up seriatim the ordinary general pathological processes as discussed in systems of pathology for it is our purpose to show the distribution of basic aberrations from the normal in terms of zoological position. To this end one must consider the response of the heart (a) to damaging influences and (b) to a demand for increased work. In the first group come degenerations and inflammations, upon which may succeed an incompetency in the form of dilatation. The response of the normal heart to any physical demand greater than customary has usually been thought to lie in the direction of hypertrophy, but on occasion it has seemed to be in the form of dilatation, especially if the strain has been sudden and severe. Starling thinks that the primary and normal reaction of the heart to physical strain is always dilatation. The idea of hypertrophy must not be confused with an understanding of the relatively large hearts in animals whose habits demand great cardiac power, for then it is their norm and might be called “physiological cardiac hyperplasia.” I shall use the terms “increased muscle bulk” and “increased chamber space” as preferable to hypertrophy and dilatation; this also focuses attention upon the two features of an enlarged heart.
DEGENERATIONS AND INFLAMMATIONS.
Degenerative changes in disease are recorded in our system as amyloid, hyaline, fatty metamorphosis, granular and cloudy degeneration. While there is perhaps between some of these conditions and true myocarditis a matter only of degree, the records have been analyzed as filed and perhaps some lessons can be learned from the responses of the various zoological orders. In the accompanying Table 1 will be found the distribution of degenerative and inflammatory lesions through the zoological orders. The percentages speak for themselves but deserve as well some consideration from the standpoint of normal heart value; this will be taken up later after the other lesions have been discussed.
TABLE 1. _Table Showing Incidence, in the Orders, of Degenerations and Inflammations, or in Other Words the Response to Infectious and Toxic Agencies._ ════════════╤════════╤═══════╤════════╤════════╤════════╤════════╤══════════ Heart of │Degener-│Myocar-│Pericar-│Endocar-│Total[7]│ Cases │Percentage │ ations │ ditis │ ditis │ ditis │ │followed│in deaths │ │ │ │ │ │ by │per order │ │ │ │ │ │dilation│ ────────────┼────────┼───────┼────────┼────────┼────────┼────────┼────────── Primates │ 8│ 12│ 18│ │ 38│ │ 7.6 Lemures │ 1│ │ │ │ 1│ │ 1.2 Carnivora │ 19│ 14│ 11│ 10│ 54│ 5│ 11. Pinnipedia │ 2│ 1│ │ │ 3│ │ _15._ Rodentia │ 5│ 7│ 6│ │ 16│ │ 8. Insectivora │ │ │ │ │ │ │ Chiroptera │ │ │ │ │ │ │ Proboscidea │ │ 1│ │ │ 1│ │ _33._ Hyracoidea │ │ │ │ │ │ │ Ungulata │ 3│ 9│ 8│ 2│ 20│ │ 5.4 Edentata │ 2│ 3│ 1│ │ 7│ │ _44._ Marsupialia │ 12│ 5│ 6│ 12│ 33│ │ 19. Monotremata │ │ │ │ │ │ │ │ │ │ │ │ │ │ Passeres │ 4│ 4│ 9│ 2│ 19│ │ 1.4 Picariæ │ 2│ 1│ 3│ │ │ 6│ 6.7 Striges │ │ │ 1│ │ 1│ │ .8 Psittaci │ 10│ 7│ 7│ │ 24│ │ 3.4 Accipitres │ 2│ 19│ 8│ 7│ 36│ 1│ 18.3 Columbæ │ 2│ 1│ │ │ 3│ │ 2. Pterocletes │ │ │ │ │ │ │ Galli │ 4│ 10│ 13│ 1│ 28│ 1│ 9.3 Hemipodii │ │ │ │ │ │ │ Fulicariæ │ 2│ │ 1│ │ 3│ │ 8.6 Alectorides │ │ 1│ 1│ │ 2│ │ 5.4 Limicolæ │ │ │ │ │ │ │ Gaviæ │ 1│ 1│ │ │ 2│ │ 10. Pygopodes │ │ │ │ │ │ │ Impennes │ │ 1│ │ │ 1│ │ 16. Steganopodes│ │ 1│ 2│ 1│ 4│ │ _20._ Tubinares │ │ │ │ │ │ │ Herodiones │ 1│ │ 1│ 2│ 4│ │ 4.1 Odontoglossæ│ │ │ │ │ │ │ Palamedes │ │ │ │ │ │ │ Anseres │ 16│ 17│ 11│ 6│ 50│ 1│ 15.7 Struthiones │ 2│ 3│ 5│ 1│ 11│ │ _34._ Crypturi │ │ │ │ │ │ │ ────────────┼────────┼───────┼────────┼────────┼────────┼────────┼────────── Total │ 98│ 118│ 112│ 44│ 367│ 8│ ════════════╧════════╧═══════╧════════╧════════╧════════╧════════╧══════════
In this and subsequent tables, figures in italics are for small groups of animals coming to autopsy, usually less than one hundred, and from which percentages may be misleading. The number of autopsies upon such groups may be found by consulting the list given on page 47.
ENDOCARDITIS, MYOCARDITIS.
Romberg said in his classical work on the heart that there is always some form of myocardial disease with endocarditis. The 44 cases of valvular disease detected at this Garden are 15 of chronic nature, 29 of acute or subacute character. In the former, the chronic, 9 showed some grade of muscular involvement, while 21 of the 29 acute cases of valvular inflammation were accompanied by myocardial damage; the percentages are 60 for chronic and 72 for acute, a relation that would be expected if one credit the theory that many valvular inflammations start at the root of the valves, but, at all events, they indicate that after the acute stages have passed the myocardial damage may be repaired.
[Illustration:
FIG. 1.—VEGETATIVE AND ULCERATIVE ENDOCARDITIS OF AORTIC VALVE. OSTRICH (STRUTHIO AUSTRALIS). ORGANISMS ISOLATED CORRESPONDED CLOSELY TO BAC. AFANASIEFFICHESTER. ]
The large number of cases of endocarditis among the Carnivora, Accipitres, Anseres and Marsupialia is noteworthy and can hardly be explained by other argument than a special vulnerability of this organ in these groups. However, the unusual number of cases in our only native marsupial, the opossum, seems worthy of a special note since ten of the twelve instances in the order Marsupialia affected this particular animal. When seen these ten cases were acute in five instances, subacute in three and chronic in two. The Streptococcus pyogenes was isolated in three of the five acute cases; bacteriology of the others was negative or not done. All of the acute and one of the subacute cases were combined with some evidence of general septicemia. The type of lesion was in no way peculiar, unless the facts that all were vegetative when acute and markedly deforming when chronic, be noteworthy. In two chronic aortic cases the valvular orifice was almost closed, yet the left ventricle could not be considered as greatly hypertrophied and no dilatation existed. In one acute aortic and mitral case, general dilatation existed. The mitral was involved nine times, three times alone, four times with the aortic, once each with the tricuspid and pulmonary. Once the vegetations were limited to the mural endocardium. Nine of these animals came from one enclosure over a period of two and a half years, during which time other opossums died from similar bacterial infections (pneumonia) despite repeated cleansing of the place. No unusual number of cases of this or similar kinds occurred elsewhere in the Garden at this time, but it would seem that we had in this cage a continued bacterial infection.
UNUSUAL PERICARDIAL CHANGES.
The appearance of a stiff gelatinous exudate in the pericardial sac has attracted our attention on ten occasions (8 birds, 2 mammals). The substance seems quite homogeneous and almost entirely acellular. One specimen became solid on heating and another became turbid when put into Kaiserling’s fluid. In two cases bacterial cultures were made; nothing grew. It has not been associated with tuberculosis or tumors nor has any one pathological lesion more than another appeared to accompany it.
A peculiar lesion occasionally seen in birds is “uratic pericarditis” a process not infectious at all, according to Plimmer, but due to renal disease. It has been seen here in association with retention of urates in the kidney, with gout of birds, and apparently quite independent of any renal or constitutional disease. Both layers of the sac are pearl gray or irregularly salted with a whitish granular material so that they are entirely opaque; occasionally the distribution is spotty. The deposit does not seem to penetrate the myocardium. There is at times some involvement of other serosæ, but this is usually much less marked than around the heart. It does not seem that this of itself should be fatal, but it has been the most decided pathological factor in some of the autopsies.
Aside from pericarditic exudates, twenty-one instances of pericardial effusion have been encountered. They offer little that is peculiar in etiology, chemistry or cytology, but as there has been some question of the position of the accumulation of the fluid in human beings, it might be well to note the position in our material. It is recognized in veterinary medicine that the cardiac dullness is increased especially to the right, and that most of the fluid will be on that side and posteriorly. At our autopsies on mammals this is the position usually occupied by the fluid, the apex being covered by pericardium, unless the quantity be great enough to make the sac taut, and this position is retained whether the animal be laid upon the one side or the other; nor does the fluid all leave the base of the heart when the body is placed prone. The crown of the heart is nearly always well covered. In birds, on the other hand, the fluid occupies the apical part of the sac, probably due to the fact that this membrane is attached by its tip to the transverse air sac wall which takes the place of a diaphragm, so that the tip of the heart is always free and the pericardium of the base fairly closely applied to the epicardium. This holds good even for the birds whose cardiac apex is normally attached to the pericardium by a fibrous band.
HYPERTROPHY AND DILATATION.
The response of the heart to a continued demand upon its working capacity will, as already indicated, lead to increased muscle bulk or to larger chamber size. Whether hypertrophy be purely the building of a bigger engine or be accompanied by, or due to, muscular disease as had been suggested by certain authors, was a question to which an answer was hoped, but it would seem that the solution is no nearer than can be obtained in human pathology. Fifteen of the 34 cases showed some degree of myocardial damage. Some of the other cases may have been instances of so-called essential hypertrophy, enlargements due to hard work or to low grade hidden infection. Aubertin[8] ascribes such cardiac muscle increase to overwork under the stimulus of intoxication from intestinal sources or from irregular constitutional functions. For information concerning this and pathological enlargements one may consult the Table (2) of Hypertrophies and Dilatations; in advance the method of charting must be known. Since it is usually impossible to decide what may be the single important factor in the cardiac disease, all of the accredited factors have been listed with the hope that the resulting figures would be significant. Thus an animal may have recorded pericarditis, nephritis and arteriosclerosis—who shall say which was primary or most potent in the cardiac change.
Essential hypertrophy is limited to those cases for which there was no concomitant pathology that might have been responsible for the overgrowth. There was one in a carnivore (fox) and one in a raptatory bird (buzzard). Idiopathic dilatations on the other hand are much more common, but they still bear a relation to the apparent vulnerability of the heart. Their distribution is as follows: Primates 1, Carnivora 1, Pinnipedia 1, Ungulata 1, Marsupialia 4, Anseres 1. These may be cases such as Plimmer described, of cardiac failure, indicated by dilatation, the result of inactivity. Besides these special instances and the ones accounted for in the list, there were three acute dilatations apparently due to shock, two ungulates and one marsupial, probably incidental to fright when being caught by the keepers.
The association of secondary dilatation with hypertrophy is only evident in three instances. One case and perhaps the most interesting, is that in which the principal antecedent pathology was thyroid hyperplasia and nephritis; the dilatation was perhaps agonal or shortly before the last struggles. It would seem that all of the dilatations occurred shortly before death because long standing passive congestions and dropsies of cardiac origin are exceedingly rare; only one certain case is recorded (carnivore).
Let us now examine the Table (2) according to orders and then as to causation. The Primates’ heart is apparently well able to increase in size in response to increased work, a demand most often made by pulmonary, pleural and pericardial diseases. Two of these cases occurred in animals suffering with pulmonary tuberculosis sufficiently extensive to impede cardiac action while in another case the tuberculous lesion was mild but a pericarditis existed. When the right hand columns are inspected it would seem that on occasion dilatation may occur; one of the tuberculous pulmonary cases had a dilated heart. The slothful lemurs apparently have no call upon their cardiac mechanism.
Carnivora with their large organ, which, it would seem, should be prepared for excess work either simply as a reserve or as an inherent ability to grow, present in about equal numbers, hypertrophy and dilatation. It is admitted that there are within this order, genera of differing habits, but analysis of the canidæ, felidæ and ursidæ for examples, in the first place, offer too few specimens for conclusions and, secondly, have upon trial actually shown nothing definite, so that we are forced to use the larger group, the order. It is interesting to note that long continued infection is in this order the most potent factor in enlargements of the heart. Four of the ten cases show myocarditis. Nephritis does not seem very important in relation to cardiac muscular increase, but occurs with great frequency in association with dilatation. Three of the cases of hypertrophy were associated with thyroid disease and two of these showed dilatation as well. The general causes of chamber distention are more diverse, and we see associations that do not appear with hypertrophy, namely arteriosclerosis and diseases of the chest.
TABLE 2.
_Table Showing Incidence per Order of Hypertrophy and Dilatation, and the Principal Associated Lesions Believed to Have Etiological Importance._
═════════════╤═════════════════════════════════════════════════ Heart of │ Hypertrophy ─────────────┼─────┬────────┬────────┬────────────────┬──────── „ │Total│Percent.│Valvular│Arteriosclerosis│Diseases │ │ for │Disease │ │ of │ │ Order │ │ │Thoracic │ │ │ │ │ Serosæ ─────────────┼─────┼────────┼────────┼────────────────┼──────── Primates │ 4│ .8│ │ 1│ 3 Lemures │ │ │ │ │ Carnivora │ 10│ 2.1│ 1│ │ Pinnipedia │ │ │ │ │ Rodentia │ │ │ │ │ Insectivora │ │ │ │ │ Chiroptera │ │ │ │ │ Proboscidea │ │ │ │ │ Hyracoidea │ │ │ │ │ Ungulata │ 4│ 1.2│ │ │ 1 Edentata │ │ │ │ │ Marsupialia │ 1│ .6│ 1│ │ Monotremata │ │ │ │ │ Total Mammals│ 19│ │ 2│ 1│ 4 │ │ │ │ │ Passeres │ │ │ │ │ Picariæ │ 1│ 1.1│ │ 1│ Striges │ │ │ │ │ Psittaci │ │ │ │ │ Accipitres │ 8│ 4.1│ │ 4│ 1 Columbæ │ │ │ │ │ Pterocletes │ │ │ │ │ Galli │ 2│ .7│ │ 1│ Hemipodii │ │ │ │ │ Fulicariæ │ │ │ │ │ Limicolæ │ │ │ │ │ Gaviæ │ │ │ │ │ Pygopodes │ │ │ │ │ Impennes │ │ │ │ │ Steganopodes │ │ │ │ │ Tubinares │ │ │ │ │ Herodiones │ │ │ │ │ Odonotoglossæ│ │ │ │ │ Palamedes │ │ │ │ │ Anseres │ 2│ .6│ │ │ Struthiones │ 2│ _6.2_│ │ │ 2 Crypturi │ │ │ │ │ Total Birds │ 15│ │ 0│ 6│ 3 ─────────────┼─────┼────────┼────────┼────────────────┼──────── Total │ 34│ │ 2│ 7│ 7 ─────────────┴─────┴────────┴────────┴────────────────┴────────
═════════════╤════════════════════════════════════════════════════════ Heart of │ Hypertrophy ─────────────┼─────────┬───────┬─────────┬─────────┬───────┬────────── „ │Pulmonary│ Renal │ Chronic │ Acute │Thyroid│Myocardial │ Disease │Disease│Infection│Infection│Disease│ Disease │ │ │ │ │ │ │ │ │ │ │ │ ─────────────┼─────────┼───────┼─────────┼─────────┼───────┼────────── Primates │ 3│ 1│ 1│ 1│ │ Lemures │ │ │ │ │ │ Carnivora │ │ 2│ 6│ 1│ 3│ 4 Pinnipedia │ │ │ │ │ │ Rodentia │ │ │ │ │ │ Insectivora │ │ │ │ │ │ Chiroptera │ │ │ │ │ │ Proboscidea │ │ │ │ │ │ Hyracoidea │ │ │ │ │ │ Ungulata │ │ 4│ │ │ │ 2 Edentata │ │ │ │ │ │ Marsupialia │ │ 1│ │ │ │ 1 Monotremata │ │ │ │ │ │ Total Mammals│ 3│ 8│ 7│ 2│ 3│ 7 │ │ │ │ │ │ Passeres │ │ │ │ │ │ Picariæ │ │ 1│ │ │ │ Striges │ │ │ │ │ │ Psittaci │ │ │ │ │ │ Accipitres │ │ 3│ 1│ 1│ │ 5 Columbæ │ │ │ │ │ │ Pterocletes │ │ │ │ │ │ Galli │ │ 1│ │ 1│ │ 1 Hemipodii │ │ │ │ │ │ Fulicariæ │ │ │ │ │ │ Limicolæ │ │ │ │ │ │ Gaviæ │ │ │ │ │ │ Pygopodes │ │ │ │ │ │ Impennes │ │ │ │ │ │ Steganopodes │ │ │ │ │ │ Tubinares │ │ │ │ │ │ Herodiones │ │ │ │ │ │ Odonotoglossæ│ │ │ │ │ │ Palamedes │ │ │ │ │ │ Anseres │ │ │ 1│ 1│ │ 1 Struthiones │ │ │ 1│ 1│ │ 1 Crypturi │ │ │ │ │ │ Total Birds │ 0│ 5│ 3│ 4│ 0│ 8 ─────────────┼─────────┼───────┼─────────┼─────────┼───────┼────────── Total │ 3│ 13│ 10│ 6│ 3│ 15 ─────────────┴─────────┴───────┴─────────┴─────────┴───────┴──────────
═════════════╤═════╤═══════════════════════════════════════════ Heart of │ │ Dilatation ─────────────┼─────┼────────┬────────┬────────────────┬──────── „ │Total│Percent.│Valvular│Arteriosclerosis│Diseases │ │ for │Disease │ │ of │ │ Order │ │ │Thoracic │ │ │ │ │ Serosæ ─────────────┼─────┼────────┼────────┼────────────────┼──────── Primates │ 4│ .8│ │ 1│ Lemures │ │ │ │ │ Carnivora │ 11│ 2.2│ │ 1│ 2 Pinnipedia │ │ │ │ │ Rodentia │ 8│ 4.2│ │ │ Insectivora │ │ │ │ │ Chiroptera │ │ │ │ │ Proboscidea │ │ │ │ │ Hyracoidea │ │ │ │ │ Ungulata │ 11│ 3.│ │ │ 4 Edentata │ 2│ _12.5_│ │ │ Marsupialia │ 8│ 4.5│ │ │ Monotremata │ │ │ │ │ Total Mammals│ 44│ │ 0│ 2│ 7 │ │ │ │ │ Passeres │ 1│ │ │ │ Picariæ │ │ │ │ │ Striges │ │ │ │ │ Psittaci │ 1│ .1│ │ │ Accipitres │ 1│ .5│ │ │ 1 Columbæ │ │ │ │ │ Pterocletes │ │ │ │ │ Galli │ 2│ .7│ │ 1│ 1 Hemipodii │ │ │ │ │ Fulicariæ │ │ │ │ │ Limicolæ │ │ │ │ │ Gaviæ │ │ │ │ │ Pygopodes │ │ │ │ │ Impennes │ │ │ │ │ Steganopodes │ │ │ │ │ Tubinares │ │ │ │ │ Herodiones │ │ │ │ │ Odonotoglossæ│ │ │ │ │ Palamedes │ │ │ │ │ Anseres │ 5│ 1.5│ │ │ 1 Struthiones │ │ │ │ │ Crypturi │ │ │ │ │ Total Birds │ 10│ │ 0│ 1│ 3 ─────────────┼─────┼────────┼────────┼────────────────┼──────── Total │ 54│ │ 0│ 3│ 10 ─────────────┴─────┴────────┴────────┴────────────────┴────────
═════════════╤════════════════════════════════════════════════════════ Heart of │ Dilatation ─────────────┼─────────┬───────┬─────────┬─────────┬───────┬────────── „ │Pulmonary│ Renal │ Chronic │ Acute │Thyroid│Myocardial │ Disease │Disease│Infection│Infection│Disease│ Disease │ │ │ │ │ │ │ │ │ │ │ │ ─────────────┼─────────┼───────┼─────────┼─────────┼───────┼────────── Primates │ 1│ │ │ 1│ │ 1 Lemures │ │ │ │ │ │ Carnivora │ 2│ 4│ 1│ 2│ 3│ 2 Pinnipedia │ │ │ │ │ │ Rodentia │ 3│ 2│ 2│ 4│ │ Insectivora │ │ │ │ │ │ Chiroptera │ │ │ │ │ │ Proboscidea │ │ │ │ │ │ Hyracoidea │ │ │ │ │ │ Ungulata │ 1│ 2│ 2│ 2│ │ 1 Edentata │ 1│ │ 1│ │ │ 1 Marsupialia │ 1│ 3│ 2│ 2│ │ 1 Monotremata │ │ │ │ │ │ Total Mammals│ 8│ 12│ 7│ 11│ 3│ 10 │ │ │ │ │ │ Passeres │ │ │ │ 1│ │ Picariæ │ │ │ │ │ │ Striges │ │ │ │ │ │ Psittaci │ 1│ │ │ │ │ Accipitres │ │ │ │ 1│ │ 1 Columbæ │ │ │ │ │ │ Pterocletes │ │ │ │ │ │ Galli │ │ │ │ 1│ │ 1 Hemipodii │ │ │ │ │ │ Fulicariæ │ │ │ │ │ │ Limicolæ │ │ │ │ │ │ Gaviæ │ │ │ │ │ │ Pygopodes │ │ │ │ │ │ Impennes │ │ │ │ │ │ Steganopodes │ │ │ │ │ │ Tubinares │ │ │ │ │ │ Herodiones │ │ │ │ │ │ Odonotoglossæ│ │ │ │ │ │ Palamedes │ │ │ │ │ │ Anseres │ │ 2│ 1│ 2│ │ 1 Struthiones │ │ │ │ │ │ Crypturi │ │ │ │ │ │ Total Birds │ 1│ 2│ 1│ 5│ 0│ 3 ─────────────┼─────────┼───────┼─────────┼─────────┼───────┼────────── Total │ 9│ 14│ 8│ 16│ 3│ 13 ─────────────┴─────────┴───────┴─────────┴─────────┴───────┴────────── For meaning of italics see foot note Table 1.
The rodents seem to have no power to increase muscle bulk, but a sufficient number of cases of dilatation occur to make one conclude that this is their method of response to unusual strain. Pulmonary disease, mostly of infectious nature, and myocardial degenerations are the principal causes.
The next order to show cardiac enlargement is the Ungulata where nephritis is the most frequent association with hypertrophy and disease of the pleura and pericardium with dilatation, or the reverse of the factor value in the Carnivora. These animals, fairly well prepared for flight, with moderately large hearts, seem more often to show dilatation than hypertrophy.
Two Edentata (armadillo) showed dilatation but no hypertrophy.
Marsupials behave somewhat like rodents in that the heart does not seem to increase muscle bulk, but our records do not explain this clearly. As already mentioned four cases had no sufficient internal reason for dilatation, but as one was probably the result of shock three only remain to be accounted for. Nephritis seemed to exist in all three, but two of them had kangaroo mycosis of the jaw and a general chronic infection.
If now our attention be given to the Aves we find the highly specialized Passeres and Striges not represented and their closely related well- organized orders Picariæ and Psittaci with only an isolated single case. This is the more interesting since the last order suffers reasonably often with arteriosclerosis. Accipitres, the birds of pugnacious habit and carnivorous diet, seem well able to increase their muscle upon demand, but do not often suffer dilatation. Vascular and renal diseases stand out most prominently in the etiology, and one-half of them show myocardial change. The Galli, which includes both ground and flying birds, are represented but fail to exhibit any unusual accompanying disease. Anserine birds apparently have a low power to increase the size of the heart, but most often allow it to dilate. Struthiones, large stalking and rapidly travelling birds, apparently have a good margin of safety in their cardiac mechanism.
SUMMARY OF LESIONS ASSOCIATED WITH HYPERTROPHY AND DILATATION.
Analysis of the associated pathology will reveal that among the mammals, renal disease, chronic infections and diseases of the thoracic serosa are most often responsible for hypertrophy, and that something over one- third of the hearts showed myocardial damage. Among the Aves arteriosclerosis and renal disease are most important in enlarging the heart; half of the cases had myocarditis. In so far as dilatation in mammals is concerned, renal disease and acute infections are decidedly more important than other influences, even than the next in order— chronic infections and pulmonary diseases; only one-fifth of the cases had myocardial disease. Acute infectious disease is the most potent cause of dilatation in birds; only two of the eight cases had degeneration of the heart muscle.
COMPARISON OF MAMMALIA AND AVES.
If a comparison of the incidence of increased muscle bulk in the two classes be made[9] it will be found to occur two and one-half times more often in mammals, while dilatation occurs nearly ten times more often among the mammals than among the birds. Hypertrophy is accompanied by myocardial change in 44 per cent. of the cases, whereas muscular degeneration was only seen in 24 per cent. of the dilatations; this change is conspicuously lacking in the Primates, Ungulates and Marsupials. The usual teaching has been that dilatation, which means enlargement of chambers and thinning of walls or at least no thickening thereof, implied an inability on the part of the heart to keep up with increased demand—a decompensation. If Starling be correct that dilatation is not a degeneration of pump value but merely one of adaptations to increased demand, then this method is more characteristic of mammals than of birds. There is, however, the reserve power to increase the muscle bulk inherent in the mammalian, not possessed or needed by the avian heart. The large-hearted class Aves certainly dilate their blood pump less frequently than mammals and indeed have less cardiac disease.
An analysis of the incidence of hypertrophy _versus_ dilatation shows that hypertrophying power resides in the Primates, Accipitres and Struthiones, their hearts relatively seldom dilatating. Lack of such power and consequent dilatation resides in Rodentia, Ungulata, Marsupialia and Anseres. Hypertrophying power lies therefore chiefly in the heart of average size for its class, dilatation occurring in the small heart. (See page 63.)
AVIAN HYPERTROPHY.
There is little to be learned from the nature and anatomy of the hypertrophies and dilatations except perhaps their character among the birds, in which the physics of the circulation is somewhat peculiar. In this class both the hypertrophy and distention are predominatingly left- sided, a state probably explained by the pressure against which the pump must work in flight because then the lungs and the viscera are somewhat compressed by the pressure of an excess of air in the pneumatic sacs. At all events while concentric hypertrophy was mentioned once, it is difficult to estimate the degree of increase in the right chambers because they are not uncommonly well filled when diastole occurs at death. Grober[10] asserts that the normally large heart (or what I have called “physiological hyperplasia”) shows a “hypertrophy” of the right ventricle because of the extra work entailed in flying. This is certainly not the case in the material we have seen under pathological conditions. Right sided increase might be expected if pulmonary or serous membrane affections were prominent, but left-sided increase, following arteriosclerosis and nephritis is the actual finding. The best examples of concentric hypertrophy are in the dogs with thyroid disease and the best examples of concentric dilatation in ungulates suffering shock.
SUMMARY.
The foregoing pathological data can now be summarized by grouping the facts under the headings of absolute and relative vulnerability of the heart. By the former is meant the actual number and quality of lesions in the various orders, but here at once one comes upon the irregularity of examples of zoological and pathological character, and if one trust entirely to the percentages, fallacious conclusions might be reached. Basing judgment upon the incidence of pathological lesions in mammals and birds, it is evident that the former has greater vulnerability, as 13 is to 6.2. This is noteworthy as we shall learn that the bird has a larger and apparently better prepared heart than the mammal. Attempts to discover the order or kind of animal having the greatest or lowest vulnerability are difficult for the reason given above. Thus, for instance, Pinnipedia, Proboscidea, Edentata, Gaviæ, Impennes, Steganopodes, and Struthiones present the highest percentages of cardiac lesions, but the total specimens examined are so few that these figures may well be misleading. (See Tables 1 and 2.) If, however, figures mean anything in such small groups, these are the animals which have the greatest cardiac vulnerability. They have little in common in regard to zoological relationships and habits; four of the seven orders are rather slothful and three are active. It is much better to limit our observations to those orders from which sufficient examples have been subjected to autopsy and upon which we have some standards for comparison in the heart-body weight ratio. It so happens that in the above seven orders I was unable to obtain any reliable figures of heart weight. Table 3 is a combination of data from Tables 1 and 2 for the principal orders from which we have enough material (at least one hundred autopsies) and for which it is possible to obtain as comparative standards figures indicating the weight of the normal heart in kilograms of body weight; Table 4 gives these ratios for normal hearts. The information about the weights was obtained from some of our own figures and the references given in the footnote.[11] There are no extensive data upon weights and measures in exact terms, such as body weight, so that we are limited to the numbers quoted in parentheses besides the orders in the table. The ratios might be modified slightly by a greater number of examples, but they show certain things by comparison of the classes; in a rough manner the heart ratios correspond to the pathology.
TABLE 3. _Table Containing a Condensation of the Two Foregoing Tables and Showing Figures for Degenerations, Hypertrophy and Dilatations for Orders Having the Largest Number of Autopsies._ ═════════════════╤═════════════════╤═════════════════╤═════════════════ │ Degenerations, │ Hypertrophy │ Dilatation │ &c. │ │ ─────────────────┼─────────────────┼─────────────────┼───────────────── Primates │ 7.6│ .8│ .8 Carnivora │ 11.│ 2.1│ 2.2 Rodentia │ 8.│ 0.│ 4.2 Ungulata │ 5.4│ 1.2│ 3. Marsupialia │ 19.│ .6│ 5. │ │ │ Passeres │ 1.4│ 0.│ 0. Picariæ │ _6.7_│ _1.1_│ 0. Striges │ .8│ 0.│ 0. Psittaci │ 3.4│ 0.│ .1 Accipitres │ 18.3│ 4.3│ .5 Columbæ │ 2.│ 0.│ 0. Galli │ 9.3│ .7│ .7 Herodiones │ 4.1│ 0.│ 0. Anseres │ 15.7│ .6│ 1.5 ─────────────────┴─────────────────┴─────────────────┴─────────────────
TABLE 4. _Table Showing Weight of Normal Heart in Relation to Body Weight. Number of Specimens used to Determine Weight Quoted in Parenthesis._ ════════════════╤═══════════════════════════════ Average Heart of│Grams per Kilogram of Body.[12] ────────────────┼─────────────────────────────── Man ( 4)│ 5.67 Primates ( 4)│ 6.56 Carnivora ( 6)│ 6.78 Rodentia ( 5)│ 5. Ungulata (10)│ 5.8 Marsupialia ( 3)│ 5.1 │ Average 5.82 Passeres (43)│ 19.8 Picariæ ( 9)│ 21.3 Striges ( 4)│ 7.33 Psittaci ( 6)│ 8.89 Accipitres ( 7)│ 12.32 Columbæ ( 4)│ 14.47 Galli (16)│ 11.08 Fulicariæ ( 3)│ 23.82 Limicolæ ( 2)│ 8.78 Anseres (14)│ 11.8 Struthiones ( 1)│ 12.7 │ Average 13.84 ────────────────┴─────────────────────────────── For meaning of italics see foot note Table 1.
However, there are many reasons why great caution should be used in evaluating the relative size of the heart. Welcher showed in his work that the proportion is greater in small and young animals than in large and adult ones. All the authors quoted agree that in birds and to less degree but still clearly in mammals, there is a direct relationship between the bodily activity of an animal and its cardiac bulk. This is fairly well shown in the list of avian heart ratios, but not so clearly in the mammals. What shall be considered the most active mammals—the monkey, perhaps, with his tendency to be occupied constantly, yet we find the greatest heart bulk among the Carnivora, animals prepared for travel and struggle, and the smallest among the Rodentia, quiet and timid animals. The avian order showing the greatest cardiac ratio, the Fulicariæ, shore birds, is made up of some quiet hiding varieties, and of some capable of very prolonged flight; the most constantly active fliers (Passeres) also have a high cardiac weight proportion. The inactive owls have the smallest heart bulk.
The contrast between the average heart-to-body weights of mammals and birds is striking, the latter having two and one-half times as much as the former, 5.8 _vs._ 13.8. Since this is the most prominent and best supported statement in the table of weights, it may be used to compare with the incidence of the pathology as seen in the two classes.
Degenerations and inflammations occur in mammals and birds as 9.5 is to 5.5.[13]
Hypertrophies occur in mammals and birds as 10.3 is to 4.3.[13]
Dilatations occur in mammals and birds as 2.4 is to .28.[13]
In other words, mammals are much more susceptible than birds to degenerative and inflammatory processes, show an ability to increase the muscle bulk two and a half times as great and are liable to chamber distention nearly ten times as often. It might also be put that birds cannot or do not need to increase their muscle, and that the chamber and muscle balance is more perfectly arranged.
While in the preceding pages hypertrophy has been discussed rather from the standpoint of its value as a compensating and reserve capacity, and dilatation as a degenerative or decompensatory process on the part of the cardiac mechanism, it may be that dilatation of the mammalian heart is the usual method employed by the class in response to increased demand. It seems certain, however, that the originally and normally larger heart, both mammalian and avian, more often uses an increase of its muscle to this purpose.
Hypertrophy was accompanied by myocardial disease in 44 per cent. of the cases, while dilatation showed this change in only 24 per cent. This supports the theory that dilatation is a normal response of the myocardium under strain and the belief held in many quarters that the muscle increases its bulk because some of it is damaged.
The differences between classes are not so conspicuous between orders. However, the large heart of the carnivores increases both its muscle and chambers, while the small heart of the rodents and marsupials more often dilates. Analysis of the avian orders is inconclusive and somewhat contradictory. Let it suffice to say that the birds which fly most, with exception of the ducks, have a relatively low vulnerability, and the soaring carnivorous Accipitres and the largest birds, Struthiones, apparently have a high susceptibility to damaging influences and enlarge their muscle bulk in response to increased work.
Aneurysms of the heart are quite rare; only two have been seen. They were both located at the apex of the left ventricle in birds; they did not rupture. Myocardial damage is evident in both cases but the cause is not clear; parasites could not be demonstrated. Plimmer reports a case of cardiac aneurysm at the apex from infestation of the heart muscle by sarcosporidia.
SECTION III DISEASES OF THE BLOOD VESSELS
The gross anatomy of the blood vascular system is constructed upon the same general scheme throughout mammals and upon a comparable basis in birds. Microscopically there is little variation throughout the orders unless it be in the relative proportion of muscular and connective tissues. The origin of the great vessels at their cardiac base and their distribution to the pulmonary and to the greater circulations in no way differ in these two classes in that it always consists of an efferent pathway to the lung and a root vessel above the aortic orifice. The former has usually quite a distinct origin on the right side, but in some birds the posterior wall of the pulmonary artery may overlie the entire aortic base; this, however, is not the rule for birds. The aorta in most mammals remains a separate and distinct vessel for some distance, after which it gives off the innominate and subclavians. In the birds on the other hand, the stretch immediately above the aortic valve is usually ballooned out somewhat, into a sort of sac or ampulla from which the subclavians and descending aorta arise. This forms a structure of rather trident shape, the lateral prongs being the subclavians, the middle and posterior being the aorta proper. In some birds the aorta may have the length of a centimetre or more then dividing into the left subclavian and right aorta from which the right subclavian comes off.
There is definitely more support to the heart and vascular roots in mammals than in birds, in the latter class these structures lying quite free between the lateral air sacs and well in front of the lungs. Nor is there the richness of mediastinal areolar and fatty tissue in the winged creatures.
The vessels of mammalia retain a considerable wall throughout nearly their entire length. At first the wall is thin compared to the calibre of the vessel while the arteries smaller in calibre, have a heavy wall. In birds the arterial stalk at the heart is supplied with very heavy walls, but after the second branching the relation of wall to calibre seems to continue about the same. In this class the stalk vessels have wall to calibre relation of 1 to 3 (measurements in 2 Passeres, 1 Psittaci, 1 Accipitres) whereas in mammals the relation varies from 1 to 5 to 1 to 7 (observations on 2 carnivores, 1 ungulate, 2 rodents). In mammals the consistency of a normal artery wall remains much the same, a firm, resilient, yellow-white tissue, quite opaque and standing open upon cross section. In birds this description covers the main stalk, the aorta in the abdomen and the first part of the carotid and iliacs. When these characters are lost, the arteries become semitranslucent bluish strands so that they are difficult to follow in the muscles of the neck and extremities. This is particularly true in the Passeres, Picariæ, Galli and Columbæ while in the Psittaci, Accipitres, and Anseres the arteries are distinctly whiter than the veins but yet quite soft. In the Herodiones and Struthiones, thick walled vessels may be followed as far as the second joint in both extremities. These differences depend in part upon the grosser construction of the central arteries in Aves and in part upon the larger amount of elastic tissue in them than in the secondaries and smaller vessels, and than in comparable mammalian vessels.
It is impracticable to go into the minutiæ of histology in the different orders, which indeed varies but little, although attention might be directed to the facts that in all central vessels the relative amount of elastica is greater than in smaller ones and that muscular tissue seems to exceed in the latter. Considerable work has been done upon the amount and arrangement of muscle bands in isolated genera, but no comprehensive data are at hand upon orders. The strands of muscle do not seem arranged so regularly as in mammals; the pulmonary artery of the cat, for example, has a muscle arranged like an oblique band in waves or festoons along the length. The mammals as a class seem more richly supplied with arteries and veins than do the birds, and the square area of the vascular system is likewise larger. This is distinctly different from the amount of heart bulk as given in the discussion of kilogram-heart ratios so that one might say that the birds are “overhearted and undervesseled.”
In so far as the physiology of the two classes is concerned it is obvious that a different regulatory system is necessary because, aside from the variations of pressure incidental to pulmonary, muscular and visceral work, there remains the altering pressure within the air sacs of Aves, a force different under states of rest, of running, of deep water swimming and of flying with or against the wind. Part of the internal air pressure variation is cared for by the ability a bird has to respire the air in its sacs and bones, but in prolonged exposure to the pressure under water or during protracted flight some compensatory mechanism doubtless exists. This seems to reside in part in the heavy elastic quality of the arterial stalk and the very rich venous supply of the abdomen, including the renal-portal system and the distensible pelvic veins. Just where the governing power for this mechanism resides is as much a matter of debate as in the case of the human being, but certain researches would place it in the caudate lobe and pituitary body.
Having discussed these general comparative data we can now pass to a consideration of the pathology seen at this Garden. The subject will be studied from the standpoint of the vessels as a system and the changes peculiar to it. Naturally the most important lesions affect the great stalks and the principal trunks, from which the processes may continue into the smaller vessels. The essential alterations are inflammatory and degenerative, of which the latter are by all odds the more important. The former are either involvements of the vessel walls by frankly infectious processes, or less easily proved to be bacterial in origin, as is the case with periarteritis nodosa. Acute arteritis and phlebitis are constantly encountered and present nothing unusual. General nodal periarteritis has been seen in the lower animals, Lupke having reported[14] before the German Pathological Society a big outbreak in cows, but it is less common than among men; we have not discovered it here.
THROMBOSES.
Thrombosis is practically always a parasitic or an infectious process although at times considerable difficulty is encountered in explaining the source of the worms or bacteria. Thus, for example, the iliac or femoral thromboses which are at the bottom of intermittent claudication, are frequently quite vague in origin. We have had one such case in a deer in which a partly occluding thrombangeitis existed in both femoral arteries and veins. Mesenteric thrombosis, a serious condition in cattle and horses from infestation with sclerostomum or strongylus, has not been proven at the Garden, but we have seen one case of numerous thromboses of the venous radicals in the jejunal wall apparently due to some nematode larvæ; the specimens were so soft by decomposition that determination was not attempted. There occurred a thrombosis of the cava and aorta originating from a necrotizing cloacitis, apparently streptococcal in nature, in a Demoiselle crane. The clot, while not totally occlusive, extended nearly as far as the heart in the vein and the abdominal aorta. There is also on record a thrombosis of the vena cava and right pulmonary vein in an American beaver, harboring Hepaticola hepatica in the liver, with a fibrosing pneumonia due to this parasite. Another case in which parasites seemed to take a hand concerned a common raccoon with tapeworms (sp.?) in the small intestine and microscopically discoverable parasitic parts in the lungs; these organs were the seat of extensive congestion and venous thrombosis, the latter containing really enormous numbers of diplococci. The parasites probably paved the way for bacterial invasion. A frank case of septic thrombotic aortitis was noted in a Rice Grackle, the infectious focus apparently being a vegetative “tricuspid” valvulitis.
ARTERITIS.
In addition to these cases, productive inflammatory changes were discovered five times affecting vessels in or near frank inflammatory processes. The animals affected with this productive process were three birds, a rodent and an elephant. In the case of two birds and the rodent the process was associated with chronic intestinal lesions, while in the elephant it was found as an endarteritis obliterans in large vessels of the lung of chronic pulmonary tuberculosis occurring in this animal. These instances serve as examples of the truly productive inflammatory processes affecting vessels and illustrate the distribution through the animal kingdom. Pathogenetically there are no essential differences, and histologically they correspond to the forms seen in man. Had every piece of tissue been subjected to microscopy wherein such lesions might have existed, more examples might have been discovered, but these processes excite no peculiar secondary effects so that attention is not drawn to them directly. The only noteworthy difference between mammals and birds is the fragile character of the clots in the latter class. This is peculiar because the principal response of this class to an infectious irritant is coagulation necrosis, liquefying enzymes apparently being absent or small in quantity.
Fatty deposits in the aortic intima are by no means uncommon in the human subject and are encountered at all ages, even in youth at a time when progressive arteriosclerosis does not accompany them. There is a belief in many quarters that this fat may be laid down and then removed. Such deposits are exceedingly rare in wild animals; when they occur it is in small indefinite patches and not the bands or rows as found in man.
TABLE 5.
_Table Showing the Incidence of Degenerative Arterial Disease, the Percentage in Animals Subjected to Autopsy and the Principal Associated Pathology._
════════════════╤═════╤══════════╤═════════╤═════════╤══════════ │Total│Percentage│ Due to │Aneurysms│Myocardial │ │ of order │parasites│ │ disease │ │ │ │ │ ────────────────┼─────┼──────────┼─────────┼─────────┼────────── Primates[15] │ 3│ .6│ │ │ 3 Carnivora │ 16│ 3.3│ 5│ 7│ 1 Ungulata │ 13│ 3.5│ 2│ │ 1 Marsupialia │ 3│ 1.8│ │ │ Total │ 35│ 1.8│ 7│ 7│ 5 │ │ │ │ │ Passeres │ 3│ .22│ │ 2│ Picariæ │ _2_│ 2.2│ │ │ Psittaci │ 13│ 1.8│ │ 1│ Striges │ 3│ 2.2│ │ │ 1 Accipitres │ 13│ 6.6│ │ 1│ 4 Galli[16] │ 5│ 1.6│ 1│ │ 4 Steganopodes[16]│ _5_│ _25._│ │ │ Herodiones │ 1│ 1.│ │ │ Palamedes │ _1_│ _20._│ │ │ 1 Anseres │ 11│ 3.4│ │ 2│ 4 Struthiones │ _7_│ _22._│ │ │ Alectorides │ _2_│ _5.4_│ │ │ 1 Total │ 66│ 1.8│ 1│ 6│ 15 ────────────────┼─────┼──────────┼─────────┼─────────┼────────── Grand Total │ 101│ 1.8│ 8│ 13│ 20 ────────────────┴─────┴──────────┴─────────┴─────────┴──────────
════════════════╤══════════╤═══════╤═════════╤══════════ │Valvulitis│ Renal │ Chronic │ Chronic │ │disease│pulmonary│infectious │ │ │ disease │ disease ────────────────┼──────────┼───────┼─────────┼────────── Primates[15] │ │ │ │ 1 Carnivora │ │ │ 1│ 5 Ungulata │ 1│ 2│ 3│ 2 Marsupialia │ │ │ │ Total │ 1│ 2│ 4│ 8 │ │ │ │ Passeres │ │ │ │ Picariæ │ │ │ │ Psittaci │ │ 6│ 3│ 2 Striges │ 2│ │ │ Accipitres │ 2│ 5│ 2│ 4 Galli[16] │ │ 2│ 1│ 2 Steganopodes[16]│ 1│ 3│ │ Herodiones │ │ │ │ Palamedes │ │ 1│ │ Anseres │ 1│ 4│ 1│ Struthiones │ │ 1│ 2│ 3 Alectorides │ │ 1│ │ Total │ 4│ 25│ 9│ 11 ────────────────┼──────────┼───────┼─────────┼────────── Grand Total │ 5│ 27│ 13│ 19 ────────────────┴──────────┴───────┴─────────┴────────── For meaning of italics see foot note Table 1.
DEGENERATIVE ARTERITIS OR ARTERIOSCLEROSIS.
Whether or not it be exact to speak of the more protracted forms of vascular disease usually called arteriosclerosis or atheroma as degenerative, such changes form the most pronounced features of the lesions, and we have made such a separation at this laboratory. Here is not the place to engage in the academic discussion of the nature of the process, but I wish to state that collectively the changes as seen in such lesions in the lower animals are more degenerative than productive, and that we have never seen true ulcerative atheroma as it not uncommonly appears at the autopsy table in any large hospital. This disease of the vascular walls has long been attributed to alcohol, gout, syphilis and other such prolonged intoxications to which we might apply the light term of “toxins of civilizations.” Too little credit, or discredit has been given to chronic intestinal disorders, overeating, and overdrinking of ordinary fluids, to entirely incorrect diets, and to chronic bacterial diseases. Even though the exact counterpart of the disease in man does not occur in lower animals, we shall see the probable association with food and with habits, in a manner discordant with former teaching of the causation of the disease.
The group to which the name degenerative arteritis has been applied is, as has already been indicated, more productive than the analogues seen in the human being, but indeed it is questionable whether the lesions even in the lower animals are not more degenerative than productive. Since, however, chronic arteritis is always associated with damage to the elastic and muscular fibres of the media as well as with fatty change and overgrowth of the intima, all the deforming and degenerative cases will be classed together.
The general picture in mammals is one of diffuse rather than of plaque- like thickening, but well outlined raised or depressed areas are encountered. In the aorta and larger branches one may find irregular streaking and loss of elasticity with fairly clear, pale yellow or gray, flat sections of distinct opacity. Rarely these may contain calcareous matter, a change most often seen in the carnivores. The lesions are very largely limited to the aorta; 26 or 76 per cent. of the 35 cases had this distribution alone. The arch seemed never to be affected alone, and indeed it is rather commoner to find opaque patches stretching along the thoracic or even abdominal portion; this is especially true of the Ungulata.
[Illustration:
FIG. 2.—ARTERIOSCLEROSIS AND ATHEROMA. THORACIC AORTA. JACKAL (CANIS AUREUS). THIS WAS CONTINUED TO THE MESENTERIC AND ILIAC VESSELS. ]
There have been also in mammals five cases of mesial change which have given rise to the picture described by Mönckeberg and usually entitled by his name. However, the noteworthy differences between the wild animal and the human cases are the absence of advanced calcification in the media under the concavities and the prominence of the changes in the aorta near the heart to be found in the former. These few cases do not permit an association of the arterial disease with any particular pathology in other parts.
Considered minutely, the outstanding lesion in the class Mammalia is the separation of the elastic fibres by fluid and debris, apparently derived from the degenerated muscle fibres, associated with a decrease of round and elliptical nuclei. Globules and hyaline pink staining material are often collected between split-up elastic strands, which fibres in some cases seem quite numerous, in others reduced. In the intima heaping-up of cells and fibres is very moderate in degree while usually one finds only subendothelial edema. When the process has advanced far, the microscopy is like that of well developed human lesions. Arterial degeneration due to parasites gives a different picture in that medial degeneration is far advanced and some fibrinocellular activity is seen upon the intima when this tissue remains. When, however, the infestation has proceeded to weaken the wall sufficient for it to give way into an aneurysm, little or no vestige of the true arterial wall is left.
In the Aves the distribution and anatomy of this process present some differences. The aorta is as usual most conspicuously the seat of change, but it is noteworthy that the dilatation or ampulla immediately above the aortic valves and from which the main vessels spring, is practically always free of lesions which are on the other hand most marked in the thoracic and abdominal sections. One’s attention is usually attracted to the aortic surface by its roughness although visibly there may be no plaques, but upon close inspection a mottled opacity may be detected. This all seems due in the few cases subjected to tissue section, to hyperplasia of endothelia, with or without fibre increase. The media may show muscular granularity or no change at all. At the stage when plaques are formed, fairly well outlined, firm but rather brittle, raised areas are detected, seated upon a distinctly opaque gray wall. The remainder of the vessel may be smooth and elastic but sometimes, in the Accipitres for instance, a general resistance to pressure and tension is found. Microscopically such a vessel will show a media the seat of ruptured muscle fibres, split-up or broken elastica and some debris, while the intima is covered with active and distinct fibrocellular exudate.
I have for comparison divided the cases into those in which the superficial productive character was prominent and those seemingly entirely a degeneration of the media, that is with inactive intima. In mammals 77 per cent. of the cases were of the degenerative type while in birds 50 per cent. were of this kind. The exact importance of this difference is not easy to evaluate, but with the facts that the bird has a greater elastic supply for its large vessels and a greater wall to calibre ratio, it is interesting. The aorta alone was affected in half of the birds, the remainder showing lesions in the carotids and femorals.
The tendency for the media to degenerate would lay the basis for concavities on the intimal surfaces after the type seen in Mönckeberg’s sclerosis. A number of cases of this variety have been encountered, but instead of being better developed in the vessels of extremities as in man they have presented more definite pictures in the aorta and pulmonary vessels. Examples will be quoted under the discussion of the various orders.
[Illustration:
FIG. 3.—ARTERIOSCLEROSIS, ATHEROMA AND ANEURYSMAL DILATATIONS IN THORACIC AORTA. WILD CAT (FELIS RUFFUS). ]
Primates are not often affected with degenerative arterial disease, two of the instances observed showing this change confined to the coronary vessels. As might be expected the myocardium in both was affected, and in one animal had a definite concentric hypertrophy. A very interesting case was encountered in a Lion-tailed Macaque (_Macacus silensis_). His heart showed distinct fibrosis of the conducting pathways from auricle to ventricle and of the papillary muscles. No atheroma was present in the aorta, but in the pulmonary distinct sacculations of the Mönckeberg type were found. Mesial degeneration was apparently responsible, but no calcification had occurred. Death was due to acute gastritis.
Carnivora present about half the cases seen in mammals and 16 per cent. of the total. Five of the sixteen cases owe their origin to parasitic arteritis and were combined with aneurysms. As will be noted by consultation of the list there is no outstanding accompanying pathology, a fact which makes parasites more important. One case of mesial degeneration, resembling the Mönckeberg type was observed in the thoracic aorta of a bear.
Ungulata are generously represented, thirteen cases being recorded distributed rather unevenly between the odd-toed (1 or 8.5 per cent.) and even-toed groups (12 or 2.9 per cent.). The single case in the first group occurred in a Zebra (_Equus burchelli_) wherein was found about the middle of the thoracic aorta a diffuse thickening of media and intima in a circular plaque approximately two centimetres in diameter; it was by no means so well developed as similar lesions in the even-toed ungulates. This recalls the expression of doubt by Zinserling as to the occurrence in the horse of arteriosclerosis similar to that in human beings.
The lesions in the Artiodactyla are both in plaques and diffuse, the aorta and its branches sometimes being quite wrinkled but beset with firm elevations with and without calcification. These changes are fairly definite and, although they never attain the development seen in man, resemble the stage of wrinkling and roughness in the preulcerative stage of the human analogue. Two of the cases were associated with dilatations of the mesenteric vessels and with periarteritis, a picture strongly suggesting parasitic infestation; in one case ineffectual search was made, in the other no record is made of the parasites. Renal disease occurred only twice and myocardial damage only once. Chronic pulmonary disease, present thrice, took the form of tuberculosis twice and pleural adhesions with atelectasis once.
Marsupialia present three quite interesting cases, a Tasmanian Devil (_Sarcophilus ursinus_) and two Kangaroos (_Macropus_). The first showed distinct sacculations in the ascending aorta, suggestive of Mönckeberg’s sclerosis but equally resembling several small or incomplete aneurysms. The underlying vessel was opaque and stiff, continuing so to the middle of the thoracic portion. The other marsupials showed distinct mesial damage with early calcification and a roughened intima; once the pulmonary artery was involved.
It will be noticed that the orders Rodentia and Lemures are missing from those showing arterial disease although we have a reasonable number of autopsies upon them.
Passeres are hardly good exponents of vascular disease, an interesting thing in view of their large heart, heavy vessels, and flying habits. It is, however, striking that two of the three birds of this group had aneurysms of the aorta, one of which ruptured just above the origin, partly into and partly outside the pericardium. Despite several microscopical sections we were unable to find the tiny ends of the breach and any evidence of parasites. In the other case a vegetative growth occurred on the intima near the dilatation.
[Illustration:
FIG. 4.—ARTERIOSCLEROSIS IN AORTA. OTTER (LUTRA CANADENSIS). THERE IS RELATIVELY LITTLE INTIMAL CHANGE, THE MEDIA BEING FIBROTIC AND ALLOWING THE INTIMA TO BE DEPRESSED IN SMALL CONCAVITIES. ]
The Picariæ were represented by a Hornbill and a Toucan. The former presented roughened yellowish elevations for two centimetres above the aortic valve; this seemed the only involvement. The Toucan had a few small scattered but deep yellow plaques in the same location.
Psittaci, although failing to be accredited with a high percentage of arterial disease, nevertheless present some striking and interesting changes. In the first place, the central vessels are not so conspicuously the principal seat of atheroma as is the case in many other orders, and the lesions are not so productive. It is usual to find flat areas of opacity, perceptible as easily by section through the wall as by holding up the opened vessel to the light, the seat of the density being in the media. This can be followed into the wing arteries and, upon microscopic section, these smaller vessels will show mesial degeneration, thus being comparable to arteriocapillary fibrosis of man. However frequent this picture may be, there are also instances of overgrowth in the intima, prominences over opacities or raised plaques at the points of branching, lesions which correspond to the activity of the inner coat. It is interesting that renal disease, chronic pulmonary and general infections occur in a goodly proportion of these birds.
Striges is an order of little importance. The lesions in the two cases consisted of rather prominent plaques in aorta and large branches.
Accipitres stand out as giving the greatest percentage of any order of which we have had a fair number upon which to make comparisons. Their arterial lesions are frequently accompanied by renal, myocardial and valvular disease. Mesial and intimal alterations are about equal in degree, irregular patches going on to softening without ulceration, and early calcification being quite prominent. The sickle at the branching of the renals is a favorite site of deposit. Like the parrots their arterial damage is not confined to the aorta, but may be found in the carotids, femorals or small wing arteries. The most common situation is, however, in the lower thoracic and renal regions.
Galli, represented by five specimens, seem to have their vascular disease accompanied very often by myocardial and infectious disease. Their arterial pathology consists of raised gray patches in the aorta only.
Steganopodes give the highest percentage among avian orders, but this must be held _sub judice_ because of the small number of specimens subjected to autopsy. Renal disease occurred in three cases. Their lesions are in the form of yellow opaque streakings in the aorta and its branches, in one case following the carotid half way up the neck. Plaques are not common, and when they occur are streaky and illy outlined.
Herodiones, represented only by a heron, are negligible. This bird showed a diffuse thickening with early thrombotic deposits attached to the intima.
Palamedes are represented by a Screamer which showed around the orifices of the renal arteries an early fatty deposit and mesial opacity.
Anseres present a considerable number of cases which are accompanied by cardiac, renal and general pathology. The character of the lesions is like that of the Accipitres and the distribution differs in only one particular. In four of these eleven cases the elevations or opaque areas were limited entirely to the stretch of aorta which might be compared to the arch in mammalia, that is the part with which the right subclavian is in closest contact and which bends almost directly backward to become the thoracic aorta. This excludes the ampulla just above the aortic valves. There seems no real reason for this and it may be accidental.
[Illustration:
FIG. 5.—AORTIC ARTERIOSCLEROSIS. SARUS CRANE (GRUS ANTIGONE). THE LESIONS ARE ELEVATED AND IRREGULAR. ]
Struthiones, with seven specimens having arterial disease in the great vessels alone, seem to have no especial characters unless these be in the heavy furrowing and stiffness of the wall, with opaque, elevated, indefinite patches, seen mostly in the descending aorta; once a long tough and partly brittle stretch was found in the carotid.
Alectorides, with a relatively high percentage, present irregularly outlined fatty and finely granular patches in the intima of the lower aorta and abdominal vessels, and, in two cases, as far as the vessels of the lower extremities could be followed.
The orders Columbæ and Fulicariæ are missing from the list of Aves having arterial disease, yet a reasonable number of autopsy records are at hand.
SUMMARY ON ARTERIOSCLEROSIS.
Having discussed the orders separately, a review of the whole situation is desirable. Chronic arteritis, or as it is usually called arteriosclerosis, is common to very many zoological orders, and its principal lesions are comparable throughout the two classes under consideration. A statement as to its incidence would best be made by adopting an arbitrary number of observations as the desired minimum upon which to draw conclusions, and I shall adopt one hundred as such a figure. Accepting this as reasonable, a review of the table indicates that the order of percentage incidence is: Accipitres 6.6, Ungulata 3.5, Anseres 3.4, Carnivora 3.3, Striges 2.2, Psittaci 1.8, Marsupialia 1.8, Galli 1.6, Primates 0.6, Passeres 0.22; the other orders have less than one hundred specimens each. There is no doubt that carnivorous birds have the highest incidence of chronic arterial disease. Next in order come three varieties with nearly equal incidence, the ungulates, anserine birds and carnivorous mammals. These orders have little in common unless it be that in nature they are often engaged in prolonged or strenuous effort, as in fight or flight. We possess no measurement of their vascular supply but by consultation of the table giving heart weights (page 63) it will be found that three of them have values below that of the class in which they belong; the Carnivora alone have a greater heart-to-body ratio than the average for its class Mammalia. Nor do these orders have any direct dietetic relationship. The expected longevity of these groups does not permit one to discover any reason for arterial changes except perhaps that they have a reasonably good viability under park conditions, and therefore many have a longer opportunity to develop vascular disease. It so happens, however, that the first four groups are the most likely to suffer from gastrointestinal inflammation, of dietetic or bacterial origin.
It is interesting, but not easily explicable that the orders of great activity, Primates and Passeres, are at the end of the list; their food is very largely carbohydrate in character. Just why Lemures, Rodentia and Columbæ should be missing is not quite clear, because orders of comparative habits and food are included.
A review of the concomitant pathology reveals the fact that nephritis more often accompanies these processes than any other single condition. Among the chronic infectious disease in the table is included chronic enteritis; this group falls well behind the renal diseases. The relatively small number of cases of valvulitis speaks rather against an active infectious origin of the vascular lesions.
ANEURYSMS.
Aneurysms have been observed all over the world and in nearly all the larger orders. The London Garden has had an unusually large number to report, the most striking being that described by Seligman in the 1906 Report of the Society, in a tiger thirteen years in captivity which had fourteen sacculations from pea to plum size scattered along the aorta. Even with the number of cases on record and those collected here it would be unwise to draw deductions as to their incidence or as to the possibilities of vascular dilatation in any given order. Horses have aneurysms occasionally, cows and dogs rarely, according to Rievel. I can, however, state that there has not occurred in our experience a large growing pulsating aneurysm in the aortic arch region comparable to the condition so well known in man. The literature to which we have had access gives a definite impression that parasitism of vessel walls is the most important factor in the causation of ectasia, and that simple non-parasitic arteriosclerosis is relatively unimportant. Two of our seven cases seem to have been free of parasites but the notes cannot entirely assure one of this. The distribution of cases at this Garden is found in Table 5.
[Illustration:
FIG. 6.—PARASITIC ANEURYSM IN THORACIC AORTA. PARADOXURE (PARADOXURUS LEUCOMYSTAX). PARTLY SACCULAR, PARTLY DISSECTING ANEURYSM WITH OPEN THROMBOSIS AS INDICATED BY THE GLASS ROD. PIECES OF WORM FOUND IN WALL. COULD NOT OBTAIN WHOLE SPECIMEN, SPECIES UNDETERMINED. ]
A dilatation of the first part of the arch in a seal to a size which might be described as an aneurysm caused us to make such a diagnosis, correctly enough from the size and shape of the vessel but possibly worthy of reconsideration in light of the fact that no damage to the wall was found. At the heart and in the descending arch the diameter measured 4–5 cm., while the first part of the aorta measured 7.5 cm. This great irregularity in width could not be found in other seals albeit this section of the arch is usually a trifle larger than its origin and descending portion. The cava in seals is also large, but in this particular animal it measured 6 cm. across at the liver where there is a normal dilatation. These two spaces are looked upon as normal reservoirs for blood during diving, but the case in question seemed to have excessive “aneurysmoid” enlargements without mural disease. London reports an aneurysm of the aorta in a seal.[17]
Aneurysms are not so common in birds, the incidence being in comparison with mammals as 1 to 2.2. Two seats are prominent for their development: the sinuses above the aortic valves and the first part of the subclavian vessels; two of the six cases occupied the first position, two the second, while one other lay in the arch of the aorta, the last in its descending thoracic portion. Those developing over the valves seem to arise from simple degenerative arteritis; those that occupy the other locations are apt to be surrounded by plaques on the intima. Aneurysms in birds reveal by microscopy some trace of all the vascular coats and seem not to construct an adventitia from surrounding areolar tissue. The veins have presented no peculiar pathology, except in tumors which will be taken up later. A Derby’s Tyran showed a phlebitis and periphlebitis of the left subclavian vein, of mycotic nature, which led to death by rupture and hemorrhage.
SECTION IV DISEASES OF THE BLOOD AND BONE MARROW
The production and physiology of the circulating blood seem closely similar in the two classes under consideration, although the anatomy is not the same in birds and mammals, variations also occurring within the latter group. Pathological responses follow comparable lines in that hemolyzing agencies, be they hemosporidia, absorptions from metazoan parasites or bacterial toxins, produce a reaction in erythropoietic centres, and positively chemotactic viruses call forth increases in the colorless elements. We have also observed a decrease of leucocytes in an Orang Utan suffering from influenza, a finding analogous to that in the human attack. There is, however, a much less ready response on the part of birds to any leucocyte-stimulating influence, in this class the mononuclears seeming to bear much of the burden assumed by the myeloid cells of Mammalia or at least appearing on the stage very quickly so that any increase of the latter is overshadowed by them. Perhaps this apparent difference may be further explained by the greater number of colorless blood cells, structures which might be called the principal secondary defences of the body and constantly at the disposal of the organism, normally present in the birds’ blood; they amount to 25,000 per cubic millimetre in birds, while in the mammals very few varieties have half this number. On the accompanying Table (6) will be found a few differential leucocyte counts now known to us.
TABLE 6. _Differential Percentages of Leucocytes._ _The Figures are based upon Counts of Two Hundred Cells upon Two Slides unless Otherwise Specified. Blood Films were taken from Apparently Healthy Animals in the Exhibition Cages._ ════════════════╤════════════╤═══════╤═══════╤═══════╤══════════╤══════════════════ Animal │ Polymor- │ Small │ Large │Eosino-│ Special │ Notes │phonuclears.│Lympho-│Mononu-│philes.│ │ │ Per cent. │cytes. │clears.│ Per │ │ │ │ Per │ Per │ cent. │ │ │ │ cent. │ cent. │ │ │ ────────────────┼────────────┼───────┼───────┼───────┼──────────┼────────────────── Potto │ 20.│ 67.│ 7.1│ 5.9│ │ Perodicticus │ │ │ │ │ │ potto │ │ │ │ │ │ Rhesus Macaque │ 30.2│ 61.4│ 5.6│ 2.8│ │ Macacus │ │ │ │ │ │ rhesus. │ │ │ │ │ │ │ (Av. 5 counts) │ │ │ │ Raccoon-like Dog│ 62.2│ 32.│ 2.│ 3.8│ │ Canis │ │ │ │ │ │ procyonoides. │ │ │ │ │ │ Swift Fox Canis│ 65.│ 18.│ 13.│ 1.│ 3 per │ velox. │ │ │ │ │cent. Baso│ Dingo Canis │ 77.│ 15.4│ 3.8│ 3.8│ │ dingo. │ │ │ │ │ │ Timber Wolf │ 76.5│ 15.5│ 3.5│ 4.5│ │ Canis │ │ │ │ │ │ mexicanus. │ │ │ │ │ │ Wild Cat Felis │ 55.8│ 34.│ 7.│ 3.8│ │ ruffus. │ │ │ │ │ │ Gray Ichneumon │ 52.6│ 44.4│ 2.3│ .7│ │ Herpestes │ │ │ │ │ │ mungo. │ │ │ │ │ │ Indian │ 66.│ 20.│ 14.│ 0.│ │ Paradoxure │ │ │ │ │ │ Paradoxurus │ │ │ │ │ │ niger. │ │ │ │ │ │ Large spotted │ 60.│ 31.2│ 1.2│ 7.6│ │ Civet Viverra │ │ │ │ │ │ megaspila. │ │ │ │ │ │ Ocelot Felis │ 79.│ 15.6│ 3.5│ 1.9│ │ pardalis. │ │ │ │ │ │ Texas Skunk │ 44.1│ 46.3│ 4.3│ 5.3│ │_a._ There are Mephitis │ │ │ │ │ │several grades of mesomelas. │ │ │ │ │ │eosinophilic │ │ │ │ │ │granulations, │ │ │ │ │ │ranging from very │ │ │ │ │ │fine to very │ │ │ │ │ │coarse. They are │ │ │ │ │ │entirely discrete, │ │ │ │ │ │however, and the │ │ │ │ │ │eosinophile cells │ │ │ │ │ │are quite distinct │ │ │ │ │ │from the │ │ │ │ │ │homogeneous │ │ │ │ │ │neutrophiles. Tayra Felis │ 75.6│ 19.2│ 4.1│ 1.1│ │ tayra. │ │ │ │ │ │ White nosed │ 60.│ 20.│ 18.│ 2.│ │_b._ The Coati Nasua │ │ │ │ │ │protoplasm of the narica. │ │ │ │ │ │leucocytes shows │ │ │ │ │ │practically no │ │ │ │ │ │stain. Mitotic │ │ │ │ │ │figures are │ │ │ │ │ │frequent among the │ │ │ │ │ │polymorphonuclear │ │ │ │ │ │cells. The small │ │ │ │ │ │lymphocytes show │ │ │ │ │ │basophilic │ │ │ │ │ │granules. Crab eating │ 45.│ 42.│ 2.5│ 10.5│ │ Raccoon. │ │ │ │ │ │ Procyon │ │ │ │ │ │ cancrivorous. │ │ │ │ │ │ Ring tailed │ 39.2│ 54.7│ 4.3│ 1.8│ │ Bassaris │ │ │ │ │ │ Bassariscus │ │ │ │ │ │ astutus. │ │ │ │ │ │ Kinkajou Potos │ 47.4│ 42.5│ 6.│ 4.1│ │ caudivolvulus.│ │ │ │ │ │ Common Raccoon │ 46.│ 42.9│ 7.4│ 3.7│ │ Procyon lotor.│ │ │ │ │ │ Texas White │ 67.│ 19.│ 11.│ 3.│ │ footed Mouse │ │ │ │ │ │ Peromyscus │ │ │ │ │ │ leucopus. │ │ │ │ │ │ Kangaroo Rat │ 55.│ 33.│ 6.│ │ 5 per │_c._ Many Perodipus │ │ │ │ │ cent. x │leucocytes were richardsoni. │ │ │ │ │ cells. │noted, with deeply │ │ │ │ │ │staining nuclei │ │ │ │ │ │filling up most of │ │ │ │ │ │the cells. The │ │ │ │ │ │protoplasm was │ │ │ │ │ │colored a deep │ │ │ │ │ │brown. These were │ │ │ │ │ │called x cells │ │ │ │ │ │pending │ │ │ │ │ │investigation. Polecat Mustela │ 42.4│ 54.6│ 2.1│ .9│ │ putorius. │ │ │ │ │ │ Common Opossum │ 44.│ 39.│ 7.│ 9.│ 1 per │_d._ Polynuclears Didelphys │ │ │ │ │cent. Mast│quite large, with virginiana. │ │ │ │ │ cells. │deeply staining │ │ │ │ │ │nuclei which are │ │ │ │ │ │in many instances │ │ │ │ │ │entirely separate │ │ │ │ │ │and distinct. Bridled Wallaby │ 58.3│ 38.8│ 2.│ 4.2│ │ Onychogalea │ │ │ │ │ │ frenata. │ │ │ │ │ │ Six banded │ 57.1│ 23.2│ 6.3│ 13.4│ │ Armadillo │ │ │ │ │ │ Dasypus │ │ │ │ │ │ sexcinctus │ │ │ │ │ │ Elephant Elephas│ 15.│ 47.4│ 7.6│ 5.8│ (Bilobed │_e._ The ordinary indicus. │ │ │ │ │ 23.8) │polymorphonuclears │ │ │ │ │(Basophile│are very few in │ │ │ │ │ .4) │number, and those │ │ │ │ │ │seen have nearly │ │ │ │ │ │all a faint │ │ │ │ │ │acidophilic or │ │ │ │ │ │basophilic │ │ │ │ │ │character. The │ │ │ │ │ │eosinophiles are │ │ │ │ │ │quite distinct and │ │ │ │ │ │their granulations │ │ │ │ │ │are large and │ │ │ │ │ │globular. The │ │ │ │ │ │cells called │ │ │ │ │ │bilobed are │ │ │ │ │ │unusual and can │ │ │ │ │ │probably best be │ │ │ │ │ │accounted for as │ │ │ │ │ │directly dividing │ │ │ │ │ │small lymphocytes. │ │ │ │ │ │The staining │ │ │ │ │ │properties and │ │ │ │ │ │shape of the │ │ │ │ │ │nuclei of the │ │ │ │ │ │bilobed cells are │ │ │ │ │ │most closely │ │ │ │ │ │related to the │ │ │ │ │ │lymphocytes. They │ │ │ │ │ │are not always │ │ │ │ │ │regular, however, │ │ │ │ │ │but may be almost │ │ │ │ │ │as irregular as │ │ │ │ │ │the polynuclears. │ │ │ │ │ │In practically │ │ │ │ │ │every instance, │ │ │ │ │ │however, a │ │ │ │ │ │connecting isthmus │ │ │ │ │ │may be found │ │ │ │ │ │between the │ │ │ │ │ │spherical nuclear │ │ │ │ │ │portions. No │ │ │ │ │ │mitotic figures │ │ │ │ │ │seen. The │ │ │ │ │ │protoplasm is │ │ │ │ │ │homogeneous and │ │ │ │ │ │pale blue or lilac │ │ │ │ │ │in relatively │ │ │ │ │ │large amount. No │ │ │ │ │ │granules were ever │ │ │ │ │ │seen. ────────────────┴────────────┴───────┴───────┴───────┴──────────┴──────────────────
It would seem, from a general observation of simple and infected wounds and from a few blood counts, that the response of leucocytes in the lower animals is greater than in monkeys and man. The ease with which animals endure a wound and the rapid local pus formation about an infection speak for an easy mobilization of their cellular defenders; their connective tissue elements seem equally well brought into play. In so far as birds are concerned perhaps the normally large number of leucocytes and the participation of local tissue cells in response to irritation is a preparatory protective mechanism because of their relatively small amount of bone marrow which may not be able to mobilize new cells rapidly; many of the birds, notably those prepared for long flight, have much of their osseous system given over to air space. The number of red blood cells is also greater in Mammalia, which show a variation from 4,000,000 per cubic millimetre in some small genera to 12,000,000 per cubic millimetre in some ungulates, while birds vary from 2–5,000,000 per cubic millimetre. Despite these fundamental differences in the classes, pathological changes of anemia, leucocytosis and leucemia are comparable; polycythemia in lower animals is unknown to me but may of course occur.
ANEMIA.
As in human pathology this condition may be divided into the group that follows some disease which damages the red blood cells or their source, called secondary, and those cases not preceded by such a condition, called primary. Formerly this latter group, known as progressive pernicious anemia, was copiously represented, but study has discovered that worms, inorganic poisons and infections can produce a picture of grave anemia so that the formerly large group has dwindled. We now conceive a primary anemia to be one without discoverable responsible antecedent pathology, therefore a disease of the bone marrow itself. There is one variety, hemolytic anemia, which seems to be an intoxication of the bone marrow with solution of red cells, but the affected tissue puts up some struggle against the poison. In another primary, the so-called aplastic anemia, no activity at all is shown by the marrow, no young cells appearing in the circulation. Clorosis, or green sickness of young persons, is a primary anemia and presents itself as a moderate cell reduction with a disproportionately low hemoglobin percentage. As a disease entity this does not occur in the lower animals, so far as I am aware, but a very few hemoglobin estimations and a reference to the literature would indicate that well marked hemoglobin anemia does occur.
In so far as the pathology of anemia is concerned we are obliged usually to judge by the appearance of the blood and tissues, the yellowish pallor of the mucous membranes, the condition of the marrow and the amount of pigment; severe rapid cases show hemorrhages and prolonged cases have fatty degeneration of the parenchymatous organs. For a decision of the primary or secondary nature we must judge the accompanying pathology and the condition of the bone marrow.
SECONDARY ANEMIA.
Secondary anemia can be laid in general to insanitary housing or inappropriate diet over a long period, to chronic bacterial infection of low grade, to the action of blood parasites or those of the bowel which either suck blood or elaborate an absorbable toxin, or to single great or repeated small hemorrhages. We shall now consider the cases at the Garden. Perhaps many other animals have had a substandard blood, but these are the cases in which the gross appearance attracted close scrutiny in this direction. London has had much anemia, probably from their reported heavy infestation with parasites, but this factor has with us apparently played a small rôle in the production of anemia.
IN MAMMALIA.
In so far as the Primates are concerned the one outstanding cause of anemia is degenerative disease of the osseous system. In both rickets and osteomalacia there is an irregular hyperplasia of the marrow, which is usually more marked in the latter. In osteomalacia one finds irregular areas of congestion or even hemorrhage besides masses of a gelatinous fatty tissue while scattered about are pink spots where the marrow is better preserved. In rickets, on the other hand, the tissue is more uniformly congested and less sharply separated from the endosteal osseoid material or the irregular epiphyseal spongiosa. The fibroid or osteoid growth of osteomalacia seems to be fairly well differentiated from the marrow tissue although it may send strands into the canal and across the spongy area. Histologically there is not a distinct difference in the appearances nor do they differ from the human analogue. In those cases which develop late in life the red cell centres are very few in number but usually active. In the blood, one finds a few nucleated and stippled cells, but not much change in size and shape of the erythrocytes.
It does not seem that the anemia can be the cause of death, for among our thirty-nine cases of osteomalacia and rickets, the prosectors have thought it of sufficient importance to record in the diagnoses but eleven times. There are usually complications of pneumonitis or enteritis to finish the animal before the poverty of the blood will do so, and our records show only a Black Spider Monkey (_Ateles ater_), a Silky Marmoset (_Leontocebus rosalia_) and a macaque (sp.?) with osteomalacia and grave secondary anemia. It would seem, however, that hemoglobin anemia must exist, for, despite one record of 40 per cent., Fleischl, no excess of pigment deposit is noted in the spleen, liver or marrow.
Carnivora have shown a moderate number of diseases of the skeleton but the occurrence of a marrow involvement seems less frank, although the anatomical changes are similar. However, there are three grave secondary anemias recorded in eleven carnivores suffering from osteomalacia and rickets. Another prime cause of low blood value in this order is gastrointestinal inflammation; in seventeen cases of anemia, of secondary nature, five showed gastroenteritis of severe grade or protracted character. Perhaps the most prolific single cause of this blood change is parasitism, six of the seventeen cases showing infestation, five of which are nematodes and two cestodes, one showing both. The details of these are worth recording. Two young Jungle Kittens (_Felis chaus_) from the same litter died of enteritis with a noticeable anemia; they harbored in their upper small intestine ascarids, and one of them had a few hookworms (sp.?). A Kinkajou (_Potos caudivolvulvus_) died from a general mild infection, emanating from a pneumonia perhaps, and showed a heavy infestation with tænia (sp.?). An American Wild Cat (_Felis ruffus_) died from acute catarrhal enteritis and anemia; the parasitological findings included Filaria fasciata, adults in abdominal and gluteal muscles, larvæ in the blood; Dibothriocephalis felis, Ascaris mystax and Uncinaria canina in the small intestines. While the blood was thin and pale and some pigmentation existed, the condition could not be called a picture of grave anemia. A noteworthy finding was the deep pigmentation of almost the entire intestinal wall. Ascaris mystax was found in an under-sized inbred gray wolf, killed because of poor coat; there was a marked anemia and atrophy of the skin. An Ocelot (_Felis chibigonazon_) gave a picture of anemia due to uncinariasis, but is not so instructive as the following. A Swift Fox (_Canis velox_) exhibited clearly a case of progressive secondary anemia from uncinaria, and the history is worthy of a brief recital.
Muscles atrophic, greenish black over abdomen. Fat absent. Lung is blotched by darker red markings where parenchyma contains distinct excess of frothy pink watery fluid. No fluid or adhesions in pericardium. Heart is contracted, and muscle is pale yellow and firm. The only abnormality consists of slight yellowing of musculature. The abdomen shows great omentum firmly adherent to fundus of bladder. No fluid or other adhesions in abdomen. The liver is normal in size, smooth in surface and has sharp edges, is friable and bright orange yellow. The section surface is glistening, smooth and dry. Organ is poor in blood content, greasy and breaks easily. Bladder is large, contents fluid green bile; duct patulous. Spleen normal. Kidney is small and smooth, diminished in bulk, normal location, smooth surface, and pale yellowish gray, consistency, soft, flabby. Ureters normal. Mouth and teeth normal. Stomach contains scanty brown fluid. Duodenum— Mucosa bile-stained, contained a solitary nematode worm. In its lower portion it becomes filled with a blackish red fluid, and its mucosa becomes studded by heavily outlined punctate hemorrhages whose positions are best seen through serosa. Jejunum similar in condition to duodenum and contains four small nematode worms. At one point, i.e., where the worm is located at beginning of ileum the blood staining of mucosa is strictly in neighborhood of the worm. Capillaries nowhere congested. Ileum contains slight amount of brownish black material, mucosa normal. Large intestine and rectum normal. Pancreas normal. Lymphatics normal. This is a case of death by anemia as result of bites of hookworms. There were certainly more than four worms present antemortem since no males were found, and this may be explained by a possible diarrhœa which has flushed them out. This idea is borne out by empty condition of gastrointestinal tract. Animal Parasites—Uncinaria canina. The four small nematode worms above mentioned conform in all respects to the given anatomical points of uncinaria. All four specimens are perfectly formed females. The location of the hooks was easily determined and established as being in the most dorsal portion of buccal cavity, and as projecting forward and ventrally in two groups of three each in same manner as described heretofore in similar infestations in foxes. The large nematode worm found in duodenum is, from its possession of three lips and its general form, an ascaris. The mustache, however, which is so commonly seen in ascaris worms from this region is absent. Postmortem blood of heart shows red cells granulated and almost worthless for histological study. Nucleated reds, however, are absent but other points valuable in settling the question of anemia cannot be determined.
Lung.—There are no abnormalities in supporting tissue. Alveolar walls are markedly congested. Bronchi normal and show no trace of larval hookworm infestation. Air sacs contain many red blood cells together with a few heart-failure-cells. Congestion of lung.
Liver.—No excess of fibrous tissue. Finer details of structure cannot be made out owing to advanced autolytic changes. The only possible pathological changes consist of localized areas where liver cells have fused to form notable masses of pink granular material suggesting local necroses. Autolysis.
Intestines.—Four sections are present and all show essentially the same character of changes. Interstitial tissue between muscular tissue and submucosa loosely arranged as though separated by edema.
On luminal side of muscular mucosa is a distinct zone of striking tawny yellow color with hematoxylon-eosin combination. This zone is smooth homogeneous and contains a few spindle and stellate cells with no capillaries and with little or no fibrillation. It abuts upon the fundi of the crypts. Interstitial tissue of mucosa is loose and infiltrated with round and spindle cells in its deeper portions. Here it is also congested but congestion is most marked toward lumen where masses of free blood cells occur in interstitial tissue, within lumina of crypts and within lumen of intestine itself; no parasites or ova are found. Epithelium of crypts has granular cytoplasm; goblet cell formation frequently seen; cilia well preserved. Edema; Subacute catarrhal enteritis Hemorrhage.
Six instances of nephritis, four parenchymatous and two diffuse, are recorded in the total of seventeen cases of secondary anemia in carnivores. Except in the skeletal disease the marrow is very mildly affected, some edema and reddening grossly and moderate hyperplasia minutely, being the only noteworthy changes.
The next order is that of the Ungulata wherein we have found but two cases of frank anemia, an Isabelline Gazelle (_Gazella isabella_) and an Aoudad (_Ovis tragelaphus_). The former had several lesions of different etiology and nature so that an impoverishment of the blood is not astonishing: parasitic (?) cyst in lung, chronic infective arthritis, calcareous tuberculosis, congestion and edema of lungs, osteomalacia, and osteofibroma of maxilla. The condition of the aoudad was too indefinite to permit conclusions.
The marsupials are represented by two common Opossums (_Didelphys virginiana_) and a Rufous Rat Kangaroo (_Aepyprymnus rufescens_), two of which suffered also from rickets. The condition of the bone marrow was unfortunately not recorded, but in other rachitic marsupials this tissue follows the changes seen in other orders. One opossum had a hypertrophic gastritis with numerous Physaloptera turgida, a worm frequently associated with chronic thickening of the mucosa; there was also an early portal hepatic cirrhosis with enlargement of the spleen.
Among the Rodentia we have had anemias in a Beechy’s Gopher (_Citellus grammurus beecheyi_) and a Southern (_Sciurus niger niger_) and Western Fox Squirrel (_Sciurus rufiventer_). The first had a myeloma also, and will be discussed later. One of the squirrels had osteomalacia, while the other suffered with diarrhœa and showed hydropic degeneration of the kidneys, conditions probably due to acute intoxication.
IN AVES.
The class Aves is represented by the orders Passeres, Psittaci, Columbæ, Herodiones, Gaviæ, Picariæ, Striges, Galli and Accipitres; the first four are well represented, but in the other orders only one or two cases have occurred. The causes of anemia in birds are essentially those discussed for mammals with the provision that greater attention must be paid to parasites, particularly those of the blood. Several slightly varying protozoa inhabit the blood corpuscles of birds, and numerous embryos may circulate after they escape from a parent lying in some organ or tissue. The rôle of blood parasites, intra- or extracorpuscular, in the cause of death or of anemia is, however, somewhat paradoxical. Plimmer seems to credit a heavy infestation with great value in the cause of death. In the human being an infestation of one cell in a hundred is a fair grade of malaria; such a relation is apparently common in birds, and we have repeatedly seen a much heavier seeding while Plimmer reports as many as 70 per cent. of the erythrocytes to be carriers of hemogregarines (he has seen 92 per cent. in reptiles). Can then the effect upon hemic function and vital resistance be great? It has been our practice to interpret the finding of circulating protozoa or of larval metazoa as merely reducing the resistance of the birds so that they succumb more readily to incorrect food, strange environment or infection.
It is perhaps well to show the state of our records in the Passeres by a table.
Passeres—Secondary anemia associated with intestinal or visceral parasites 11
blood parasites 9
intestinal inflammation 6
skeletal diseases and chronic infection (osseous) 3
nephritis 4
miscellaneous and unassociated anemias 8
(entries in this line not included under any other heading)
Total cases 37
In the first group, two of the birds showed cestodes, one a tænia, the other not examined for identification; three showed coiled filaria in the air sacs, two, tropidocerca in the proventricular wall and five had coiled filaria in the serosa of the stomach. The second group was infested five times with Halteridium and five times with embryo filariæ. Anemia was associated with gastrointestinal inflammation alone only once, the remaining five cases having other finding of greater significance. The three birds of the next group concerned one with tuberculosis, one with mycosis and one with a long continued abscess. It seemed worthwhile to separate four cases of anemia in which nephritis was a prominent association, in three indeed being the only other diagnosis. While it is impossible to state that either is dependent upon the other, and they may of course be coincidental, it is nevertheless noteworthy that such an obscure relation occurs here as well as in human pathology. In one of these birds seen recently there was in all probability a distinct hemoglobin anemia suggested by jaundice, pallor of the tissues, absence of pigmentations and the finding of large pale erythrocytes in the heart blood. The last group is a mixed one including some birds in which only anemia was diagnosed, others with prolonged hemorrhages, two tumors, intestinal sand, congestion of the lungs and the like.
The parrots and their relatives are represented by nine specimens, among which two had proventricular spiroptera, two had long standing tuberculosis and two had osteomalacia. The notes of the other three are not sufficient to warrant deductions.
Herodiones showed eight cases of anemia, five herons, one bittern and two storks. Parasites are noted in only three examples, herons, and it is noteworthy that these all had flukes in the proventricle or intestine; one also had ascarids in the proventricle. Two of this order suffered with long standing inflammation following bone injuries. Perhaps the outstanding features of this order are the erythrocytic picture and the condition of the spleen. The red blood cells seem very fragile or soft, for one often encounters in their fresh or stained preparation vacuoles or rifts in the protoplasm surrounding the nucleus. At first we thought these were hemosporidia, but repeated attempts at their coloration and the absence of pigment granules seem to warrant an assumption that they are artefacts. In five of the seven instances there is very definite evidence of present or past activity of the spleen. We have not always considered it sufficiently prominent to call it a splenitis, but follicular activity is commonly discoverable, and two cases of definite fibrosis are recorded. The sun bittern (_Eurypyga helias_) showed a chronic interstitial nephritis in the atrophic stage. No other of the wading birds showed secondary anemia. There are seven cases among the pigeons (Columbæ) where anemic tissues attracted our attention. Three were associated with osteomalacia, in one of which the marrow picture was that of an aplastic form being everywhere pale and flabby without cells under the microscope; it is further interesting in this case that there was a distinct but ineffectual attempt at bony regeneration by the periosteum. In another case, this time brought to death by an enteritis and cloudy swelling of the viscera, the marrow was hyperplastic and red, there being activity in the basic staining areas of the head and in the shafts. (Notes of the third case scanty.) None of the seven cases seems to have been associated with animal parasitism; one had tuberculosis. The other cases are obscure and not definitely connected with other pathology.
Ten more cases of anemia were scattered among seven orders. There is nothing striking or even individual about them worthy of special mention.
SUMMARY OF SECONDARY ANEMIA.
A review of our records shows that among 5365 animal autopsies we have recorded anemia of probable secondary character in 122 instances, 53 (2.8 per cent.) mammals and 69 (1.9 per cent.) birds. The orders represented, with the percentage for the order, are Primates, 25 or 5 per cent.; Carnivora, 18 or 3.7 per cent.; Ungulata, 3 or .8 per cent.; Marsupialia, 4 or 2.2 per cent.; Rodentia, 3 or 1.5 per cent.; Passeres, 37 or 2.7 per cent.; Psittaci, 9 or 1.3 per cent.; Herodiones, 8 or 8. per cent.; Columbæ, 7 or 4.7 per cent.; Picariæ, 2 or 2.3 per cent.; Striges, Galli, Gaviæ and Accipitres, each one case. A consideration of their associated pathology reveals the fact that four changes are prominently associated with secondary anemia, to wit: gastrointestinal inflammation, 26 times (15 mammals and 11 birds); parasitism, 29 times (7 mammals and 22 birds); osteomalacia, 24 times (18 mammals and 6 birds), and nephritis, 18 times (12 mammals and 6 birds); a few of these cases overlap, but this is rather the exception than the rule, and this does not militate against the importance of the connection with anemia. It will be noted that practically all the important orders of animals are represented, including species from all over the globe. There is, however, no especial relation of anemia to the kind of diet or digestive tract. Conclusions as to the meaning of these figures of incidence are hardly justifiable. In so far as the blood picture is concerned we can only record the qualitative appearance and the effect upon tissues. It cannot be stated that to external observation a secondary anemia presents any distinguishing features that a specimen in poor condition may not exhibit. The monkeys formerly dying of tuberculosis had not infrequently pale buccal mucosa and skin around the eyes, but upon examination of their viscera, blood or marrow the quality of their blood could not be called greatly substandard. Slide smears of secondary anemia in many specimens would occasionally show stippling or a moderate number of nucleated cells with anisocytosis and poikilocytosis. This is much more frankly exhibited in the Aves, wherein displaced karyolytic or pyknotic nuclei are very common. Mention has been made of the rifts in the protoplasm, seen in Herodiones, and this has been observed in other orders. Perhaps the most striking change is the increase of young erythrocytes and of thrombocytes in the winged creatures. The nucleus of the former reminds one of that of the human plasma cell.
The condition of the bone marrow corresponds with fair accuracy to that which one is accustomed to see in the human being. Certainly this holds good for the mammals, while among the birds, the few observations upon which we feel like relying indicate a nodular erythropoiesis of rather striking character. In the areas of reddening as seen grossly there will be found under the microscope an orderly arrangement of large red cells with loose chromatic nuclei about a very much larger cell of the same type, apparently the primary erythroblast. Outside of this group, red cells such as appear in the circulating fluid, are rather irregularly distributed in a marginal zone. I have seen small areas like this in apparently normal marrow, but the central grouping was not so large as in the anemic cases; it thus appears that we probably have the anatomy of erythropoiesis.
The deposition of pigment in the birds is in much coarser granules than among the mammals, in the former case large masses sometimes obscuring several liver cells or apparently blocking a lymphatic sinus; the Kupffer cells do not seem to be heavily laden.
The extramedullary formation of blood cells has been a matter of considerable interest and study in the human being, and as far as it concerns the circulating mononuclears, the general opinion seems to be that such a histogenesis exists. A decision in the negative is perhaps reached by the majority in the case of erythropoiesis, and as far as my observations go, this holds for all mammals. It seems worth while, however, to record an occasional finding in some birds, especially anemic ones, which may be of importance in their erythropoiesis. The adult red cell is a clearly formed ellipse with a distinct, deeply stained, sharply outlined nucleus of a shape corresponding to that of the whole cell. Young red cells have a more nearly circular outline but almost truly circular nucleus, the short diameter being at least proportionately greater than is the corresponding short diameter of the whole cell; this is also the nucleus whose internal structure resembles that of the human plasma cell. Groups of such cells have been seen in the interstices of the liver, sometimes as many as twelve, in a rather orderly formation. An excess seems at times visible in the spleen but not in orderly arrangement. Observations are under way toward determining the relation of this finding to the amount of marrow, the condition of the blood and the habits of the bird.
Primary Anemia.
As already specified primary anemia is apparently causeless, aside from the assumption that it is a disease of the marrow itself. Since there are only four cases, representing three orders and they cannot be grouped as could the secondary variety, the individual instances will be discussed separately.
Ring tailed Bassaris (_Bassariscus astutus_). Adult died after two weeks’ stay in the Garden with a history of general failure of condition. The diagnosis at autopsy was primary anemia, fatty degeneration of the liver, hemorrhages in intestines and spleen, hyperplastic bone marrow. The external appearance is of general good condition, fair skin, mucous membranes pale. Lungs collapsed, and gray-red. There are several small hemorrhages scattered irregularly throughout respiratory tissue. Lymph Nodes—small, soft mottled gray- red. Pericardium had slight excess clear fluid, and no adhesions. Heart normal in size, and of pale brown color. The liver of normal size, smooth surface and sharp edges, of a pale brown color, soft and friable. Has indistinct markings like yellow brown mottlings on section surface. gall-bladder contains some viscid brown bile. Spleen, normal or slightly less in size, consistency firm, capsule pale pearl gray, apparently not thickened. There are numerous small hemorrhagic spots on section surface. Interlying pulp is homogeneous deep red. Follicles not visible. Kidney, normal in size and shape. Trabeculæ faint. Capsule smooth, strips easily, smooth surface, and brown. Consistency soft. Medulla prominently striated, cortex homogeneous salmon pink. Stomach contains a little glistening mucus. Mucosa pale, flat yellowish, slightly opaque. There is a recent clot lying in some mucus just above pyloric valve. There is, however, no open vessel nearby. From pylorus to anus lumen contains some rather fresh smeared out or slightly clotted blood and mixed in with mucus. Mucosa is flat translucent, submucosa slightly injected in a mosaic fashion, otherwise gut wall is negative. No recognizable food present. Follicles not visible. Mesentery glands small, soft, pale yellow. Bones seem entirely normal. Marrow of long bones is firm, bloody. Marrow of ribs also deep red. Blood in intestinal tract is probably a recent slow oozing from intestinal walls, and was probably the last straw. Cause of this anemia could not be determined. Blood preparation not made because it was too long after death. Liver shows moderate fatty infiltration of marginal areas. Pigment is scarce, only a few granules being present in the Kupffer cells, not more than is often seen without marked anemia. There is a slight increase in interstitial nuclei but not in fibres. No obstruction or increase of bile ducts.
Kidney.—Very mild swelling of tubular epithelium but no exudative processes. Glomeruli show a few vacuoles but capsular space is negative to pigment. Bone marrow (Femur) fairly cellular in construction, but fat well mixed. Cellular areas well arranged, active, most of cells are small members of the larger mononuclear variety. Small lymphocytes abundantly represented. Most of the larger cells are non-granular, with centrally placed nucleus. Megakaryocytes fairly numerous, nuclei seem closely jammed into centre. No recognizable certain nucleated red blood cells, moderately number stippled cells, few adult red cells. Eosinophiles and basophiles quite few. Pigment small quantity.
This is a case of primary anemia of moderate severity and short duration, and probably of hemolytic character if one may judge by the bone marrow, although excessive pigmentation of the liver and kidneys was not found. Unfortunately the spleen was not minutely studied, nor was the central nervous system investigated. Atrophy of the intestinal tract did not exist.
Two cases occurred among the monkeys, but one example will answer, since the two were essentially the same.
The case to be cited was that of a Japanese Macaque (Macacus fuscatus). ♀ Young, weight three pounds two ounces, exhibited in the Garden about four months, and apparently in good shape until two weeks before death when it rapidly became emaciated.
DIAGNOSIS.—Aplastic anemia, chronic atrophic gastritis. Atrophy of heart muscle, fibrosis of liver, slight local cloudy swelling of liver. Perilobular diffuse nephritis (subcapsular type). Congestion of spleen. Fibrillar fibrosis of spleen. Hemosiderin pigmentation of spleen. Local amyloid infiltration of spleen. Calcareous infiltration in medulla of adrenal.
Coat only fair, body emaciated. Pale muscles, fat scanty. Respiratory tract normal throughout save for slight emphysema. The Pericardium showed no fluid or adhesions. Epicardium glistening and slightly thickened. Heart pale in color. Abdomen shows no fluid or adhesions. Liver slightly decreased in bulk, smooth surface and sharp edges, hard, and rusty brown. Gall-bladder distended, contained green fluid. Spleen firm and normal in size. Capsule smooth, shape normal. Section surface, dark reddish brown, trabeculæ distinctly visible. Kidney, normal in shape, capsule smooth, strips easily, smooth surface, glistening, pinkish gray, consistency hard. Section surface, poor demarkation between cortex and medulla. R. Adrenal, thick orange yellow cortex, solid small brown medulla. Mouth and teeth normal. Stomach distended, contains gas and small quantity yellowish mucus. Mucosa everywhere normal. Postmortem blood examined, stained by Romanowsky, but red cells were disintegrated possibly by laking so examination is not satisfactory. Histological Sections: Heart shows normal epicardium quite free of fat. Myocardium peculiar in that fibres immediately under epicardium show marked broadening in a very narrow rather sharply indicated zone where nuclei are extremely large although not especially chromatic. Transverse markings here easily, although faintly recognized, have very indefinite borders, their longitudinal fibrillæ being ranged in form of a coarse reticulum. This comes about from frequent and extensive lateral anastomoses with fellow fibres giving appearance of a syncytium. In deeper parts, fibres are of more normal size but nuclei are still large and fibres, now cut in transverse section do not appear to anastomose so freely; there appears to be a slight excess of fibrous tissue in their deeper parts. Arteries quite normal. Atrophy with regeneration.
Liver.—Capsule and interstitial parts on whole normal. Perilobular fibrous tissues largely missing, but where remaining show an overgrowth occurring in peculiar zonal arrangement and of old adult almost hyaline type. Its fibres are often arranged strikingly in whorls. Bile ducts, arteries and veins quite normal. Parenchymal cells of normal size, finely granular, prominent normal nuclei and contain small quantities of finely granular, golden brown pigment not really as abundant as commonly seen in severe anemias. Blood capillaries narrow, contain small quantities R.B.C., and Kupffer’s cells very frequently contain fine granules like those of parenchymal cells but of a greener tint. In a few isolated areas parenchymal cells distinctly more swollen than others and many show disintegration of nucleus. Hemosiderin pigmentation. Perilobular fibrosis. Slight local cloudy swelling.
Kidney.—Capsule smooth, interstitial fibrous tissue of organ proper highly fibrosed in peripheral parts, but slightly in deeper. No lymphocytic infiltrations anywhere or sclerosis of vessels. Tubular epithelium highly atrophic in subcapsular regions where tubules are narrow. In deeper parts epithelium is at times so swollen as to occlude lumina, where they are coarsely granular and occasionally show some karyolysis, a pink hyaline or finely granular material. Tufts never show fibrosis, normal size. Bowman’s capsule heavily thickened. Chronic diffuse nephritis (subcapsular type).
Spleen.—Slightly hyalinized capsule, normal thickness. General reticulum of pulp slightly fibrosed and poor in lymphocytes. Sinuses broad, crowded with red blood cells, but only small numbers of lymphocytes. Coarse granular blood pigment abundant, showing greenish cast on focusing. Malpighian follicles normal size, slightly fibrosed, and in several instances show a deposit of smooth pink material between cells. Congestion. Fibrillar fibrosis. Hemosiderin pigmentation. Local amyloid infiltration.
Adrenal.—Organ appears normal in all respects save for presence of a few small irregular areas of calcification in medulla. These occur apart from any recognizable necrotic or fibrous areas. In one place one appears to lie within lumen of blood vessel. No fibroses or special congestions anywhere in organ, and cells show normal details and normal numbers of vacuoles. Calcareous infiltration of medulla.
Stomach.—Muscular tunic normal. Submucosa thin, has densely arranged bundles of smooth, pink character. Mucosa distinctly thinned, shows comparatively few regions holding acid cells, consisting for most part of peptic type of gland. These are short and of broader calibre towards lumen than deeper, suggesting a hyperplasia of luminal portions; stroma richly infiltrated with lymphocytes, not fibrosed or congested. Epithelium of crypts has rarefied appearance, shows no special degenerative changes. Chronic atrophic gastritis.
Bone marrow appears as widely separated large, fat globules with intervening granular edematous material and no hematopoietic elements. Blood capillaries numerous and highly congested.
Although the notes fail to discuss the gross appearance of the bone marrow, the amount of alteration in its microscopy and the relatively small output of pigment in the liver, seem to substantiate the determination of aplastic anemia; it is unfortunate that the blood smears could not be used in the decision. At all events the condition of the intestinal tract, of the heart, liver, spleen, and adrenal, justify us in classing the case as one of primary anemia. The next and last instance is of the same type, although I am inclined now to differ from the diagnoses made at the autopsy table, that of aplastic anemia, and to place it in the hemolytic variety. The rapidity of the fatal attack, the redness of the marrow, the excessive pigmentation, and the prominence of recent degenerative lesions in the organs are much more like the changes of a primary hemolytic intoxication than of an aplastic anemia.
Gray Fox (_Canis cinereo_). ♂ Weight four pounds, adult, was in the exhibition two years, but in good condition until two weeks before death, when it stopped eating and rapidly fell away.
DIAGNOSIS.—(Aplastic) Primary anemia. Zenker’s Hyaline of heart and skeletal muscles. Mucoid degeneration of bone marrow. Congestion of bone marrow. Atrophy of hemopoietic elements in bone marrow.
Hemosiderin pigmentation of liver. Atrophy of liver. Congestion of liver. Congestion and fatty infiltration of kidney. Patulous lumina in adrenal and absence of pars glomerulosa.
External appearance of coat good. Decomposition advanced in intestines. Skin and subcutaneous tissue faintly yellow. Poorly developed, dark muscles and fat. Respiratory tract normal throughout. Pericardium glistening, transparent, and pale, with no adhesions. Heart a little too pale, consistency slightly soft. Normal or slightly increased size of liver, with smooth surface and sharp edges, consistency friable, and of a brownish red with rusty coloring. Spleen normal. Kidney normal in size, shape, location, and consistency. Capsule strips easily, and of a faintly yellow, under general red, coloring. Adrenal normal. Mouth and teeth normal. Stomach, serosa and wall normal. Mucosa shiny, autolytic, muddy red. Ileum, agminated follicles swollen. Feces from colon examined microscopically. Pancreas normal. Bone marrow tibia and femur gelatinous and red, not slightest trace of yellow. Blood films from heart’s blood show poikilocytosis and anisocytosis; only one nucleated red.
Microscopic Notes.—Heart has torn but normal pericardium. No abnormalities of interstitial tissue or vessels. Fibres of normal width but show transverse markings irregularly since cytoplasm becomes hyaline and swollen in many places along its course. Nuclei prominent, slightly pyknotic. Zenker’s Hyaline.
Bone marrow consists of a matrix of granular or fibrillar mucoid tissue within the delicate reticulum of which highly developed capillaries are placed, together with stellate spindle and sealring cells. In a few places only are myelocytes recognizable and then in decreased numbers. Plasma cells sometimes found containing much blood pigment.
Liver.—Capsule normal; perilobular fibrous tissue only slightly overgrown, moderately infiltrated with lymphocytes and heavily with blood pigment. Arteries, ducts, veins, normal. Parenchymal cell a little smaller than normal with nuclei of normal type, and crowded with fine granules of blood pigment. Latter lie in usual pericanalicular position. Blood capillaries narrow, moderately congested and Kupffer’s cells also contain abundant pigment granules.
Thyroid.—Interstitial framework shows no fibrosis or cellular infiltrates. Blood vessels normal. Acini fairly uniform in size, none ever attaining large proportions, but some being distinctly below normal. They are uniformly filled with a very pale pink hyaline material which in some way gradually increases in color intensity toward one side, attaining in a few examples usual intensity of colloid. Lining epithelium is low cuboidal, shows no special hyperplastic features or atrophy.
Kidney.—Capsule normal. Interstitial tissue normal. Blood vessels slightly congested. Tubular epithelium granular, disintegrated and frequently contains numerous fat globules and obscured nuclei. Lumina of about normal size containing variable quantities of pink granular detritus. Glomerular tufts normal in size and appearance. Subcapsular space and Bowman’s capsule normal.
Adrenal.—Capsule and pericapsular tissue normal. Parenchymal cells throughout poor or practically free of vacuoles, such appearing in only limited portion of pars vesicularis. Interstitial framework and vessels normal. Structure of columns in pars vesicularis is peculiar in that they extend quite to capsule with no intervening pars glomerulosa, and again in that most peripheral parts are expanded at times showing a lumen, while deeper parts show broad cells extending fully across the column. Pars reticularis contains no pigment and medullary cells quite normal. Skeletal muscles show comparatively few fibres with transverse markings. Most are swollen, hyaline, lumpy, and have pyknotic nuclei. Interstitial parts show no inflammatory change.
Tissues treated by Prussian blue test for iron. Kidney, adrenal, heart found to contain none. Spleen, liver contain abundance. That in spleen responds to test showing that it is all iron containing. Two kinds of pigment found in liver. In periphery of lobule as much contains iron as that which does not, while in deeper parts iron predominates. Many times both kinds are recognized in one cell. On the whole it is the finest granules which contain more iron (are bluer) while iron free pigment occurs in bile canaliculæ. That in Kupffer’s cells stains strongly blue.
SUMMARY OF PRIMARY ANEMIAS.
A review of these instances of grave anemia brings one to the conclusion that there is a strong similarity to the disease in man. Perhaps we have constructed a picture that is too narrow for the animal kingdom in general, but surely these few instances deserve to be distinguished from the secondary cases already presented if for no other reason than that no associated etiological condition was exposed. It was hoped in studying the anemias of lower animals, and this hope extends over all the subject of this book, to be able to throw some light upon causation. The thought of incorrect diet came at once, but we are confronted with the paucity of cases among our records. Moreover, secondary anemia from digestive and dietetic troubles is clear, but how we can use this argument for an essential change in hematopoiesis and natural hematolysis, is far from evident. It will be noticed that I have studiously avoided grouping any case with parasites among the primary cases, nor will there be found any evidence of generalized infectious disease. Most of the reported instances of pernicious anemia in the lower animals have been associated with one or other of these factors, although certain authors (Kitt, Hutyra and Marek) maintain that a causeless variety probably exists.
LEUCEMIA.
This condition is fairly well recognized by veterinarians as occurring among domesticated animals, but in the records of this Garden it has occurred rarely, indeed only once in a mammal and but five times in birds. It is interesting that, in the wealth of material at the disposal of Plimmer and his associates, only one case, a polecat with lymphatic leucemia, is noted, and but very few avian instances. Herewith is submitted the protocol of our single mammalian case; perhaps we have missed others of a mild grade dying during the early stages because their resistance to infection was reduced. Unfortunately, perhaps because of the postmortem changes, but more likely because it appeared at first as if we had to do with a case of generalized tuberculosis, the bone marrow in this case was not examined. Nevertheless the infiltrative character of the lesions, the absence of distinct tumors and the numerous mononuclears in the blood as seen in sections seem to justify a diagnosis of leucemia, in all probability of the lymphatic type. There follows this case one with similar gross and microscopic picture which has no visible increase of leucocytes, but a very distinct myeloid picture in many places.
Common Opossum (_Didelphys virginianus_). ♂ Adult. No evidence of illness. Found dead. Lymphatic leucemia (involving all viscera and lymph nodes). Diffuse nephritis. Both lungs have become entirely involved in a firm, gray-yellow mass not adherent to any serous surface. Practically no normal lung tissue is left. This seems like tuberculosis but no tubercle bacilli could be found in a good smear. Estimation of the normal cubic capacity of an opossum lung was made to be about five cubic inches. In this case not over one-half cubic inch remained respirable. Bronchial lymphatic glands were enlarged, firm, yellow gray, with no recognizable lymphatic tissue. Heart muscle was firm and flaccid, pale and striated. Liver very large, firm and tough, with smooth surface and sharp edges. Color pale brown. Section surface glistening, dry, smooth, opaque. Common bile duct patulous. Spleen, slightly increased, firm, tough consistency, capsule smooth. Section surface, smooth, firm, brown-red, pale pulp, prominent follicles, and trabeculæ faintly visible. Right kidney, slightly decreased, normal in shape. Capsule smooth, strips with difficulty, tears surface. Surface, granular, color brown, consistency firm. Thickness of cortex, narrow irregular, markings irregular and obscure. Small mass of fibrous material in cortex about 3 × 3 mm. like those in lungs. There are also numerous pale yellow gray areas in cortex and outer medulla, round and streaky, distorting the striated architecture. Right adrenal converted to a yellow gray mass like lungs. The mesenteric and retroperitoneal lymph nodes are firm, gray-yellow. This includes those under diaphragm and around cœliac axis.
The histology of the organs may be described together. The infiltrate described is a densely packed mass of large cells with large, well staining nuclei and a very narrow rim of protoplasm. It is not limited by any definite wall or septa. It has no interstitial tissue. There is no blood supply in the densest masses but the walls of the blood vessels remain intact wherever the mass surrounds them. In the lungs it has involved all structures indiscriminately, and has destroyed practically all of the respiratory surface. It seems to follow by preference the peribronchial space. A few glands may be seen in the centre of this mass, but they are rapidly undergoing degeneration. In the liver the infiltrate is chiefly beneath the capsule extending inward but a very short distance. There are no large masses as in other organs but small infiltrates are seen at the portal areas. The spleen shows a diffuse excess of pulp cells and many of the cells above described, the difference being only in the size of the nucleus which is smaller in the pulp cells. There are very small round cells relatively. Follicles are absent, connective tissue not altered. Note states follicles prominent; this is due to nodal hyperplasia of the large mononuclears above described. The parenchyma in the kidney is anemic, the epithelium is slightly pigmented but this is probably not abnormal. Between the tubules especially of the outer layer of the medulla and medullary ray but also in the cortex and around the glomeruli are diffuse, irregular, infiltrating masses of the cells as described above. In some places in the kidney hyaline casts are being formed probably due to the degeneration of the epithelium by pressure. There are a few distentions of the tubules. The capsular space is free. In the neighborhood of the collections the capsules are a trifle thicker than normal. Lymph nodes, similar to spleen in that most of the bodies are thoroughly overrun with the large mononuclears. The sinuses, both marginal and internal, are practically obliterated by these cells. In the blood vessels of the lungs and liver there are many large mononuclears, perhaps not as large a number as might be seen in leucemia, but decidedly in excess of normal.
Common Marmoset (_Callithrix jacchus_). ♂ Adult. Had cage paralysis for two months before death and declined gradually from that time.
DIAGNOSIS.—Bronchopneumonia. Myeloid hyperplasia of bone marrow. Myeloma in pancreas. Fatty degeneration of liver. Constipation. Nematodes in cecum. Animal is thin, skin bare in spots. Both lungs are pale pink with large areas of deep red consolidation. Heart is dilated, increased in size with firm, red-brown muscle. Liver is firm, red-brown, with smooth surface and sharp edges. Section surface is glistening, smooth and moist. Lobular outlines are clear by reason of pale lines. The gall-bladder is normal in size and contains fluid pale green bile; duct patulous. Spleen is normal in size, smooth capsule, soft, purple pulp, follicles small and faint, trabeculæ fairly prominent. Kidneys normal in size and shape. Capsule smooth. Section surface smooth and brown and firm. The glistening section surface has a narrow cortex, swells slightly, with prominent striæ. Intestines throughout are pale on serosa. Wall thin. Mucosa flat, pale pink. Contents creamy mucus in the upper intestine. Large intestine contains large masses of very firm feces. Cecum is distended with feces and a great quantity of nematode worms. They are not attached to mucosa nor does mucosa seem altered because of their presence. Skeleton and muscles.—Long bones of extremities break easily, but with snap. Skull can be dented with fingers. Bone marrow of femur bright red.
MICROSCOPICAL NOTES.—Liver shows moderate degree of fatty degeneration with capillary congestion. Kidneys negative. Some postmortem change in last two organs. Spleen, marked congestion. Hyperplasia of large lymph cell type, particularly in follicular centres. Blood destruction moderate. Bone marrow seen in condition of marked activity of myeloid type. Aside from enormous crowding of strands there does not seem to be any atypical cell. Intestines show practically no change. Same condition holds in pancreas. In several places in pancreatic ducts cross sections of nematodes may be found. In among lobules of pancreas is a well encapsulated cellular mass without particular architecture. It consists of cells of large lymphocyte or endothelioid series. There are numerous cells of size and staining characters of small lymphocytes. There are no megalocytes but there are some indistinguishable from myelocytes. This may be an intrapancreatic lymph node. One small lymph node found in section; it shows a picture quite like the marrow except for megalocytes. Blood vessels do not show an excess of leucocytes in free or coagulated blood.
Perhaps this latter case belongs to the aleucemic leucemias or pseudoleucemias. These two conditions are recognized by the difference in circulating leucocytes, a piece of information not at our disposal. The whole subject of hemato-lymphatic affection must remain unsettled in so far as a diagnostic name is concerned, for in very few cases has the blood of our animals at autopsy been in a state permitting reliable observations upon stained smears, because of coagulation, lysis or decomposition. After considering a few more of the diseases of the blood and marrow, the lymphatic apparatus will be considered. But there is a borderland to which a word might be devoted at this time, that group to which various names—Hodgkin’s disease, pseudoleucemia, general adenopathy, adenie, aleucemic leucemia—have been applied and which has been accepted as occurring in the domesticated animals. Since I have been occupied for several years in a study of this clinicopathological complex in the human being, such cases have been searched for most diligently, but without success. The New York Zoological Park records a case of Hodgkin’s disease, without specifications, in 1901, and at the London Garden a pseudoleucemia was found. The paucity of leucemia and of the aleucemic adenopathies in lower animals and their relative frequency in man excite speculation as to their interdependence; but more of this under the lymphatics.
AVIAN LEUCEMIA.
The class Aves is rather better represented in the group of leucemias, but here the well known infectious disease may confuse the picture. The birds affected were Psittaci 3 (1 parrot, 1 parrakeet, and 1 amazon), Herodiones (stork) 1, and Galli (Gambel’s quail), 1. There was no close association of these cases either in time or housing. One of the parrots and the stork had a picture suggesting that given by Warthin for avian leucemia while the remainder presented greater evidence of a generalized infection, such as Moore described, associated with the finding of the B. sanguinarium; this organism was isolated once, but no secondary cases succeeded upon the death of this bird. It seems hardly profitable to quote protocols of this relatively unimportant condition, especially since it is fairly well known.
The separation of the two groups just specified might be discussed, however, for it is by no means certain that they are or are not different. When a pathological picture of leucemia gives a decided impression of an acute infection there are very prominent involvements of the viscera but no lymph nodal masses. On the other hand, in the cases with nodular masses corresponding to the scanty lymph tissue of birds, there is much less infiltrative involvement of viscera and less parenchymatous degeneration. This suggests that they are different processes, but an analogous contrast may be found in the pathologic anatomy of acute and chronic leucemia in man, and I am inclined to view them as stages of the same disease. In one of our infectious cases noted above the lesion was certainly myelogenic for the infiltrate in the organs and the cells in blood smears showed an enormous number of eosinophilic and basophilic polynuclears greatly in excess of normal. The study of two of our cases confirms the picture as given for lymphatic and myeloic leucosis by Ellermann[18], but material corresponding to his lymphoidocytes or erythroleucotic group has not come to our attention. Cells with deeply staining basophilic protoplasm and a lymphoid nucleus are certainly to be found with reasonable ease in the avian marrow normally and, more than this, can be detected by careful search in nearly all cellular infiltrates of organs not leucemic in nature. Perhaps, as Ellermann states, they are collateral stages in normal erythrogenesis.
THE BONE MARROW.
Since the foregoing conditions so vitally concern the bone marrow, it is but natural to give to this structure a separate consideration. From what is known of the origin, physiology, anatomy and regeneration of the marrow from the work of Ponfick, of Neusser, Bunting, Selling, Werigo and many others, it seems highly probable that the principal conclusions reached in the study of human medicine and experimental pathology, apply to the whole group of animals here under discussion. The peculiar arrangement already mentioned as encountered in the marrow of birds differs little if any from the erythropoietic centres seen in man after experimental anemia, although it may be somewhat more orderly. Myeloblasts or megakaryocytes are not numerously present in any order, but seem more prominent in the mammals than in birds. In so far as the mononuclear groups are concerned, one can state with reasonable certainty that they differ little throughout the animal kingdom. They occur in islands, strands, or infiltrate—like groups, are mixed granular and non-granular in character and, with exception of the frankly oxyphilic cells, are distinctly basic in tinctorial affinity. In a case probably myeloma, soon to be discussed, there is not a single acidophilic or multinucleated cell to be found in two sections. As might be expected from the greater eosinophilic content of the circulating blood in the Aves, greater numbers of such cells are to be found in the marrow and they are, understandingly enough, sometimes found in distinct nodes and groups containing mono- and polynuclear varieties. Concerning the platelets, no sufficient data are at our disposal to warrant a general statement. In the avian marrow they can be made out quite clearly, as in the blood, and have a greater diameter and a sharper, more chromatic nucleus than in the higher mammalian blood. Mast cells are quite common in lower mammals and birds, in whose blood they maintain an appreciable percentage, while in the marrow they stand out clearly. It is noteworthy, in the light of Graham’s statement that the hemic basophile is but a degeneration form of the eosinophile, that in the bird’s marrow, large mono- and polynuclear cells with both kinds of granules easily may be found by Romanowsky stain. An increase of eosinophiles, seen in avian as well as in human parasitism, is not necessarily accompanied by basophilia.
Hyperplasia and atrophy of marrow in the lower mammals follow much the same conditions as in higher groups. During acute general infections, as by the paracolon bacillus in carnivores, it is common to find a distinct increase in the mononuclear centres, while in suppurative lesions a polynucleosis results. The bird, however, responds less readily with leucocytes, judged by cross sections of blood vessels and the activity of the marrow. The latter may show a myeloid picture, but mononuclears without granules, with deeply staining nucleus and protoplasm, are usually more numerous; two cases recently studied, one of tuberculosis and one of pneumonia with general congestion, had similar bone marrow— pale homogeneous red with distinct mononucleosis, more outspoken, however, in the former case. Pigment is not common in the avian marrow.
The relation of the marrow to general conditions has been mentioned in the foregoing pages, but perhaps the following diagnoses will illustrate other connections seen among our records:
Bactrian Camel (_Camelus bactrianus_).—Hydatid disease of lung and liver. Hemorrhagic enteritis. Atrophic bone marrow. Calcified areas in thyroid.
American Gray Wolf (_Canis mexicanus_).—Cretinoid. Hemorrhagic external pachymeningitis with craniotabes. Secondary hyperplasia of thyroid with colloid. Chronic lymphatic hyperplasia. Chronic interstitial nephritis. Chronic enteritis. Osteogenesis imperfecta. Hemorrhagic bone marrow. Concentric hypertrophy and dilatation of heart.
MYELOMA.
Perhaps no pathological condition has given rise to more varied opinions than the tumor-like hyperplasias of the bone marrow, growths resembling bone sarcoma with and without giant cells—myeloma, chloroma, pseudoleucemia ossium and many others. In brief only two cases occur in our series which could be admitted to this category. There have been osteomata, but they were so clearly local tumors that they cannot be included in myeloid neoplasms that are assumed to be systemic in nature. Here is not the place to engage in a discussion of the correct classification and nomenclature since there are included only the aleucemic newgrowths usually assumed to originate from blood-making cells. The first case seems to be a myeloma because of the involvement of many bones and the infiltrates in the liver. Judging by the cross section of blood vessels there is no leucemia, but of course this is not final, although somewhat supported by the normal size of the spleen and lymph nodes; lymphatic structures need not be enlarged in myeloid leucemia although they usually are.
Beechy’s Gopher (_Citellus grammurus beecheyi_). Adult ♂ . Gradual loss of power in limbs beginning about two weeks ago. No other symptoms.
DIAGNOSIS.—Multiple myeloma. Anemia. Acute parenchymatous nephritis. Chronic ulcerative gastritis.
External Appearance.—General condition fair, hair in good condition. Fully developed animal. Muscles contained no fat.
Respiratory Tract.—Thymus, large soft gray homogeneous. Both lungs are distended, pale, homogeneous, yellow pink, boggy, do not crepitate, but contain no edema. Lymph nodes, small soft anthracotic. Pericardium contained no fluid.
Abdomen.—No adhesions. Size of liver normal or slightly small, firm and pale brown-red. Architecture irregular showing areas of perfect homogeneity and others where lobules are clear outlined by paler interstices. Gall-bladder distended, contains brown fluid. Common bile duct, patulous. Spleen, normal or slightly small, consistency soft, capsule smooth, location normal; section surface, homogeneous pale pulp, faint trabeculæ. Kidney normal in size and shape, capsule smooth, strips easily, smooth brown surface; section surface glistening, opaque; consistency firm; thickness of cortex normal and of medulla normal; homogeneous cortex, glomeruli not visible.
Adrenal.—Narrow, brown, opaque cortex; pale brown, opaque medulla. Bladder, small quantity of cloudy urine showing albumin, bile and many granular casts, few hyaline casts. Teeth carious broken; mouth pale. Stomach distended; serosa and wall pale, contained gas; mucosa pale, flat, translucent except in pyloric segment where it is slightly thickened, irregular, opaque and there are several saucer shaped depressions covered with black, shiny material; these seem like sluggish ulcers. Intestinal tract throughout seems normal save for its pallor. Few natural fecal masses in lower gut.
Skeleton and Muscles.—All bones are irregular in thickness, very brittle and show in their length irregular swellings made up of periosteal growth and probably increase in marrow. The latter is pale yellow with punctate hemorrhages. Skeleton seems too soft to give support, but there is little deformity.
Microscopy.—Bone section shows a myelomatous growth of costal marrow, new myelocytes predominating. The cells are packed in disorderly fashion through the marrow. They are chiefly lightly granular but a few distinct promyelocytes are found. The hyperplasia is invading cartilaginous bone with absorption. In some places cartilage is of fetal type. Perichondrium is active but there is no round cell infiltration. Ossification is imperfect at costochondral junctions. Kidney shows granular and vacuolar degeneration of epithelium with flattening of tubular lining. Nuclei are for most part normal. Epithelium of tufts and Bowman’s capsule is likewise granular and vacuolated. Distal and discharging tubules seem to be most affected. No well defined casts are found.
Liver.—The fine markings mentioned in the notes correspond to areas of infiltration of large pale mononuclears without granules. There is no fibroblastic or polynuclear increase around them. Very small necroses seen in hepatic lobules. Very slight increase of connective tissue is noted.
This seems to be a tumor of true myelocytic origin; none of the cells was of the plasma type as usually depicted. The second case stands in the files as a myeloma, yet the full description and slides have been mislaid. It is cited briefly for record.
Samoli Ostrich (_Struthio molybdophanes_). Adult ♂ . Would not eat for three weeks.
Diagnosis.—Tuberculosis of lung, liver, spleen, kidney, mesenteric and cervical lymph glands. Myeloma of periosteum of pelvis.
Skeleton and Muscles.—Large tumor mass lying on inside of pelvis measuring about ten inches by twelve inches with a thickness of about four inches. It is sharply defined and separated from adjacent muscle by a capsule. Inner border is directly below the peritoneum, and outer border lies directly on bony pelvis. Traced to its origin it seems to come from pelvis yet tumor peels off bone easily, leaving a rough surface. The tumor is soft and succulent, of a red gray color and contains some fat and much irregularly placed masses of bony tissue.
SECTION V DISEASES OF THE LYMPHATIC TISSUES INCLUDING SPLEEN
Since we have followed diseases of the blood from the simple anemias to a place where mononucleosis in the circulatory system and in the fixed tissues is the prominent feature, another step reaches the area whence most of these cells emanate—the lymphatic system. The anatomical and physiological position of the lymphatic circulatory apparatus is closely analogous in the classes under discussion, and it stands in an anatomico-clinical sense, closer to the hematopoietic system than to any other structures, throughout the whole animal creation. This anatomical division of the circulation is closely comparable, for pathological purposes, in the mammals whereas in the birds one finds noteworthy variations. In the class Aves lymphatic radicals are extremely numerous, the plexuses in the extremities and thorax perhaps being complemental for the rather scantily supplied blood vessels. About the fibulo-tibial and femoral muscles the tiny lymph vessels form an extraordinarily dense and intricate lacework, a replica of which may be found in muscles of the upper limb, while in the pelvis and thorax a rich plexus is distributed around both kinds of blood vessels and also lies within the walls of air sacs. The air sac walls in the chest display lymphatic lines very well in birds that have been for many years exposed to railway dust, the natural pearl gray glistening membrane looking as if black pepper had been evenly dusted over it. The lymph glands or compound nodes so easily discovered in mammals are practically absent in birds. Along the large thoracic vessels and in the pelvis of some anserine and struthious varieties, small illy defined masses of lymphatic tissue may be discovered by careful search but they do not possess nodal arrangement and capsule. Lymph follicles on the other hand, are quite numerous in the respiratory, and especially, the intestinal tract. Groups of follicles may also be found in the lining of the upper ends of these tracts in such situations that the names faucial, pharyngeal, or even tubal tonsils are justly applied. I do not find any reference to a lingual tonsil in birds, but this structure is found, with of course many modifications, down as far as the monotremes. The lymphoid tissue of the nasopharyngeal region is so placed in animals as to be exposed to aerial and food infections, just as it is in man. It is, however, noteworthy that chronic inflammations leading to hypertrophy or to obstruction have not come to our attention. There is only one diagnosis of chronic tonsilitis in our records, a determination based upon the nodular red-brown prominence of the tonsillar region, but there were no true hypertrophy and areas of fibrosis combined with necroses as seen in human medicine; this case concerned a Chacma baboon.
HYPERPLASIA.
In so far as the reaction to infectious or toxic agents is concerned there seems to be a fairly uniform character through the mammalian groups, but in the Aves there are a few differences worthy of mention. It is at once admitted that these observations upon birds are based upon a very few sections of isolated lymphatic tissue, but they are supported by records of the changes in nodes in mucous membranes and viscera, and by those in the spleen. The first and perhaps most noteworthy difference is in the paucity in birds of large mononuclears of the endothelial type. Their position in chords, sinuses and germinal centres is taken by deeply staining mononuclears, of the size and general character of large lymphocytes as seen in the blood. The hyperplasia in the follicles is much more dense but it is outdone by that in the chords. Since the nodal tissue of birds is not so sharply delimited by some sort of capsule, it is but natural that the hyperplasia should be diffuse; in the intestinal wall it may extend laterally twice or thrice the width of the normal follicle. Necrosis, unless the disease be mycotic, tuberculous or parasitic, is uncommon.
It may be well to discuss for a space the reaction to infection of the thoracic and intestinal lymphatics in mammals. The amount of lymphadenoid tissue in the mediastinum is very great in some mammals, notably the Ungulates, while in others, the Rodents and Primates, for example, it is not so plentiful. Nevertheless the gross and minute changes are usually of the edemato-exudative type—large, pink, soft, moist glands. In the abdomen, on the other hand, one usually finds well outlined, firm, yellow nodes in the mesentery and behind the peritoneum. This is not only to be discovered in various chronic diseases of the intestine but even in acute, so-called toxic enteritis seen in carnivores from food poisonings. One must therefore ask if the local nodes abundant in the intestinal mucosa do not take up the poisons which cause the acute hyperplasia and are in turn backed up by the stalk glands. Even in so acute and overwhelming a disease of the intestine as hog cholera (which we have not had here) the glands retain their general structure, although hemorrhagic, while in late stages they become firm, sharply outlined and pigmented. In birds there may be swelling of the omental bursæ, but as there are no lymph glands no masses are found.
The response on the part of the lymphatic tissues as a system, or some large section of this system, is shown in the following figures. It is our practice to include in the diagnosis general acute or chronic lymphadenitis or inflammation of a large drainage area. Acute changes have been mentioned 103 times, in which the important orders are represented as follows: Primates 21, Carnivora 46, Ungulata 15, Rodentia 3, Marsupialia 13, Pinnepedia 4. Chronic changes are mentioned 43 times as follows: Primates 7, Carnivora 19, Ungulata 14, Marsupialia 1, and Pinnepedia 2. This great proportion among the Carnivora does not indicate that they have more lymphatic structures for such an advantage is probably possessed by the Ungulata, but perhaps should be interpreted as an evidence for this order of the ready response to irritation on the part of the tissues in question. They probably suffer more, as we shall see later, with inflammation affecting drainage tracts. The hyperplasias or inflammations included in the figures above most often accompany gastroenteritis, pulmonary diseases or long standing infectious processes such as arthritis, while there are also lymphatic enlargements both local and general, associated with skeletal degenerations (rachitis-osteomalacia) and with thyroid disease. The former may be described as lymphadenitis, the latter as lymphatic hyperplasia.
Unlike lymphadenitis, a condition associated with some definite infectious or toxic cause, systemic hyperplasia of the lymphatic tissue may be apparently primary and causeless. In a pathological and clinical sense alike these hyperplasias are protean in their manifestation, making a satisfactory classification extremely difficult. For our purposes they are divisible into acute and chronic, associated with an increased number of circulating lymphocytes and without such a lymphocytosis.
The first, acute systemic lymphatic hyperplasia, is known in man as status thymicolymphaticus, a well recognized condition chiefly encountered in youthful males having some of the stigmata of the opposite sex. There is no record, nor have I any recollection of a pathological state in a wild animal comparable to this condition.
If acute generalized lymph node increase be associated with lymphocytosis, acute lymphatic leucemia exists; there is no case in our records. Chronic enlargement of lymph nodes with increase of circulating mononuclears is chronic lymphatic leucemia; a case of this has been cited under leucemia.
LYMPHOMATOSIS.
Chronic enlargements of the lymphatic tissues without leucemic blood present a bewildering number of varieties, the best known names of which are Hodgkin’s disease, aleucemic leucemia, pseudoleucemia and lymphomatosis. On occasion they are at first localized tumors, being generalized only late in the course; under these circumstances they are usually classed with neoplasms in the form of leucosarcoma and lymphosarcoma. Examples of lymphatic disease answering the above description are limited to two, but even these must be explained in certain particulars. There has already been quoted under leucemia a case of a common Marmoset (_Callithrix jacchus_) which was probably aleucemic leucemia of the myeloid variety; the enlargement of lymphatic nodes was trifling. The case to be cited answers in most respects to the descriptions of systemic lymphomatosis, but there were found two conditions, enteritis and parasitism, which might be responsible for sufficient general toxemia to stimulate lymph nodes and follicles to a state of active growth. Even accepting these two cases as examples of this group, it is very plain that chronic systemic primary lymphatic hyperplasia is an exceedingly rare entity in wild animals. There has been no case resembling Hodgkin’s disease of man.
California Hair Seal (_Zalophus californianus_). Young ♂ four months old. Appeared to be in good health, no loss of flesh or activity.
DIAGNOSIS.—Lymphomatosis. Fatty degeneration of kidneys. Emphysema. Chronic follicular and catarrhal enteritis. Nematodes in intestines.
External appearance good. Both lungs distended and are tense; it seems almost like a spastic dilatation—a simple emphysema—beneath pleural surface are many minute petechiæ. Lung mottled red and gray. This color is present on section. Lobules clearly outlined and separable with fingers. Bronchi and vessels widely open, the latter containing small amount of fluid blood. Lymph nodes—Mediastinal, tracheal and those visible in neck are variously but definitely enlarged, firm, irregular and roughly nodular, both in appearance and to touch. On section they are red and gray, follicular border not preserved and merging with medulla; connective tissue visible; gray juice expressed. Pericardium normal. Epicardium, glistening, transparent and pale. Heart position, size and interior normal. Abdomen contained no adhesions or fluid. Pale brown-red, firm liver with smooth surface and sharp edges; markings not clear; section surface smooth; watery blood expressed from section. Gall-bladder normal, contents limpid, brown. Common bile duct patulous. Somewhat enlarged spleen, soft, yet resilient; capsule smooth; section surface pulp homogeneous brown- purple; follicles gray, slightly enlarged, clear, sharply outlined; trabeculæ faintly visible, more prominent where they are near follicles. Kidney normal in size, shape and location, with smooth, pale brown surface; capsule smooth, strips easily, section surface glistening, consistency soft yet resilient; thickness of cortex slightly wide, of medulla normal; individual lobules clear yet no increase of connective tissue between; pyramids quite pale; top of medulla a little darker; cortices, pale, striæ quite faint and seem irregular; glomeruli not visible. R. Adrenal—In upper pole are two cysts about 1.5 and .8 cm. across; no scar at this point. L. Adrenal— Wide pale purple, regular homogeneous cortex under very dense capsule; medulla reddish brown, homogeneous, quite bloody. In left adrenal is a pale gray, fairly well outlined area between medulla and cortex at upper pole about 3 mm. across.
Stomach.—Contains glass and stones; mucosa, soft, smooth, flat, yellow and pink, translucent rugæ; cardia about normal; pylorus, valve prominent but probably not hypertrophied. Duodenum—Beginning at pylorus and extending through to ileum where follicles commence, intestine contains small amount white, creamy material, serosa negative, mucosa smooth flat, pale pink, translucent. There are small nematodes, probably uncinaria, some of which are attached quite firmly. Here and there throughout the gut are bits of thickened mucosa or submucosa, 2–5 mm. across. Some of these have a tiny opening from which clear fluid can be expressed. Ileum shows smooth flat translucent mucous membrane; empty; individual follicles faint but discernible. Colon reddened mucous membrane, nematodes and little mucus. Pancreas, soft, normal in size and position, color pink gray. The lymphatics of peritoneal cavity are all enlarged; most of retroperitoneal are also. Regional lymph glands are also enlarged. The description given for mediastinal answers here. The glands of mesenteric stalk present chain of sausage-like masses. Glands in mesentery are but slightly affected. Glands within and without peritoneum at kidney are especially enlarged. Large gland behind stomach and pancreas and in front of upper end of spleen is much enlarged, thick and roughly circular; it shows much fibrosis. The regional glands are distinctly enlarged but proportionately not so much as the internal ones. Smear of juice expressed from peritoneal glands shows large and small lymph cells in about proper proportions. There are a few plasma cells. No granular cells.
Smear from bone marrow shows enormous number of premyelocytes and mast cells. Polynuclears in their early stages are not numerous. Small groups of lymphocytes, lightly packed together, noted here and there. Blood smears unsatisfactory.
Microscopical.—Lung shows distended vesicles with considerable congestion of septa and in some places red blood cells in alveoli.
Kidney.—Glomeruli contracted, relatively anemic; capsule negative; epithelium throughout in state of granular degeneration probably fatty; connective tissue not increased.
Intestines.—Show slight hyaline change in muscle fibres and nodular degeneration and disappearance of protoplasm, leaving bare nuclei and outline of the cells; submucosa loose; mucosa shows infiltration of round and plasma cells, diapedesis, degeneration and desquamation of epithelium. Section of ileum shows a hyperplasia of lymph follicles with active centre in which large endothelial cells predominate. Small swellings in submucosa consist of chronic granulation tissue, but there is no foreign body and no evidence of preëxistence of a lymph follicle.
Lymph nodes loosely arranged but in places solidly small lymphoid; chords and sinuses contain chiefly small lymph cells in which are some mast and plasma cells; follicles small and loose, and centres contain chiefly large lymph and plasma cells; connective tissue not increased yet there are some fibroblasts in follicles.
Spleen.—Shows almost entirely hemorrhagic pulp; blood destruction not active; follicles large and made up of about equal mixture of small lymph, plasma and large lymph cells; connective tissue prominent probably because of excess of blood around it.
LOCAL HYPERPLASIAS.
In this group and touching the purely hyperplastic, come the hypertrophies of the lymphadenoid tissue of the nasopharynx; this can be disposed of by stating that no true chronic hypertrophies have been seen. With most cases of gastroenteritis in ungulates, and many in carnivores, there is a swelling and redness of the tonsillar region but an exudative or necrotizing process does not occur.
THYMUS.
The thymus is rarely visible in our specimens but when found has usually been normal. An increase in size and a decrease of consistency of this organ is noted in marasmus (inanition) from failure of care of the young by the parent, but so far as can be determined this has not been adequate to cause tracheal compression. In a few cases of rachitis in the canines, the organ is large and pale along with the rest of the lymphatic system. In one of the tumors of the mediastinum to be discussed, the suspicion arose that the growth originated in the thymus; adenomata and sarcomata have been described in the lower animals.
TUBERCULOSIS.
Tuberculosis of the superficial lymph glands is rare as an independent lesion in the lower animals. Dr. C. Y. White was fortunate in seeing a monkey with a chain of fibrocaseous nodes in the cervical region, upon which before death he offered the suggestion that it was of tuberculous nature. In Primates almost all drainage glands exhibit some miliary or caseous process. One monkey rejected upon the tuberculin test had what was apparently a primary lesion in the glands at the tracheal bifurcation. In the Ungulata, lymphatic tuberculosis assumes two forms, the caseous and the cellular. The former is generally understood while the latter is more uncommon. It is occasionally seen in the “fungous tubercle” of cows, but we have seen it in deer and in another order, Carnivora. In the latter, tuberculosis being uncommon, examples in the lymph nodes were noted but twice, once caseous and once solid; this latter was made up of firm, homogeneous yellow pink masses of glands in the mediastinum, showing under the microscope solidly packed epithelioid and giant cells.
Lymphatic tuberculosis in the birds is rare; only one case is recalled (unfortunately record cannot be found) as small yellow, discrete firm nodules in the mediastinum and neck. The minute picture was of a solid arrangement of large vacuolated mono- and polynucleated cells which were so packed with bacilli that the preparation could not be decolorized.
TUMORS.
The neoplastic enlargements are represented by a lymphosarcoma of the mediastinum in a Dorcas Goat; there were secondary growths in the liver, the kidney and several isolated lymph glands. Secondary growths from original tumors not in the lymphatic system are curiously rare, certainly much less frequent than is found in the human being. In ninety-two tumors which are known to give metastases, only three involved the lymphatic glands and only one of these could be considered as involving nodes not in the ordinary drainage pathway.
THE SPLEEN.
The spleen is an organ whose exact position in the scheme of things remains mystifying through the whole series of animals. Its functions have been arrived at largely by exclusion, somewhat by conjecture and speculation, while the acceptably proven duties are indeed few. Although this is not the place to enter into a discussion of all the points at issue concerning the anatomy and function of the organ, a few facts might be mentioned of comparative and perhaps pathological value. While the spleen has been looked upon always as the origin of blood cells in the embryo, cases in man are on record where no spleen was discovered, a condition suggesting that its absence is not incompatible with life; that such is the case is obvious for experimental or therapeutic removal of the organ is well known.
It was suggested by Virchow that at times the spleen assumes the duty of the bone marrow and the swelling of the viscus in certain anemias seems to support this statement. However, there is no physical relationship between the size of the animal and that of the spleen, nor between the available quantity of bone marrow, the obvious richness of circulating blood and amount of lymphatic tissue. This is well shown in the water mammals which have a great deal of blood in vessels and viscera yet their spleen is relatively smaller than birds of somewhat comparable size (the ostrich, for example). The Carnivora and Rodentia among the mammals, have quite large spleens proportionately, while comparable birds, Accipitres and Striges, have relatively small ones, and an absolutely small amount of marrow.
Another anomalous example of the function of this tissue is found in the hematopoiesis of birds. While there seems to be some evidence that in the spleen and liver red blood cells may be formed, there is perhaps at most times sufficient bone marrow to keep the blood cells at a proper number. There is no inverse relation between the amount of bone marrow and that of splenic bulk; that is in diving birds with their hollow bones the latter is no greater than in gallinaceous birds which have abundant marrow in all the skeleton.
It has been suggested that the spleen supplies an activator for pancreatic ferments. This receives a sort of support from the greater size of the organ in carnivores and smaller relative size in ungulates, since in the former concentrations of digestive enzymes are more often needed. Because of the greater excretion of iron in splenectomized animals or those being starved, Fischer has thought that the spleen has some power to metabolize this element; this receives some support from the statements concerning the size of this organ in the carnivorous orders. From experimental studies it appears that some relation exists between the lymphocytes and resistance to implanted tumors. If one apply this idea to the amount of lymphatic tissue and the incidence of spontaneous new growths, it is found that no definite relationship is discoverable either in terms of size of spleen or richness in lymphatic nodes. Carnivores, rodents and marsupials show a high tumor incidence and have a good lymphatic supply. Aves, on the other hand, with a poor nodal apparatus and a variable splenic bulk, show many fewer tumors than do the mammals. The mononuclears of avian blood rise normally as high as 60 per cent., of which 40–45 per cent. are of the small size.
The size of the spleen is subject to great variation not only within orders but actually within genera; it even seems that one sometimes sees two or three members of a species kept in the same enclosure, maybe with the same disease, maybe without any obvious disease, yet with definite variation in the size of the organ. This irregularity is recognized by veterinarians (Hutyra and Marek) who ascribe it to some unknown disease, past or present, and to normal variation. The lack of uniformity is seen more clearly in birds than mammals. In the former it might be due at times to low grade or inactive parasitism or, conjecturally, to toxins from incorrect diet; we shall see later that infection and intoxication seem to have a different effect. Some writers have mentioned the possibility of an idiopathic splenomegaly (?), a condition associated in youthful human beings, with anemia and lymphadenopathy, and occasionally going over into a sort of leucemia. The existence of such a condition is difficult to admit or deny; we have met nothing which could not be aligned in some fairly well defined group. Birds have a relatively larger spleen than mammals and in addition the organ seems to respond more actively in infections or intoxications, since it may reach, under active stimulation, a size ten times that of the normal organ.
ENLARGEMENTS OF SPLEEN.
Acute enlargements of the spleen, be they of congestive or “inflammatory” nature are quite common among the lower animals, a fact that is recognized in veterinary medicine. Congestions of the spleen are most often seen during acute infections and diseases of the heart and liver. The diagnosis has been made among mammals proportionately more than in birds, 27 or 1.5 per cent. to 35 to 1 per cent.
REASON FOR CONGESTIVE ENLARGEMENTS.
Perhaps this is partly due to the circulatory anatomy since in the former the arterial and venous supply is usually by one large vessel of each kind, whereas in birds the splenic branch of the cœliac axis breaks up into several small arteries and the venous return is accomplished by numerous venules some of which reënter the posterior cava almost directly, others joining with the mesenteric to form the portal; by this arrangement a more elastic system is assured. The same condition is found when analyzing the records of chronic passive congestion; in eighteen recorded cases, fourteen were mammals and four birds. In these cases the principal associated pathological lesions were pleural and pulmonary in seven, cardiac in three, renal in three and hepatic in four. While the anatomy of the splenic blood supply may help to explain the small number of congestions in Aves, it will not answer for the inflammations which occur in large numbers in this class; this will be discussed in the following pages.
Hemorrhage and infarction of the spleen are not very common, there being eleven of the former and ten of the latter and all occurring with the same indication or history of infectious disease; in one case, an opossum (_Didelphys virginiana_) an injury probably caused a massive hemorrhage shaped like an infarct. It is, however, curious that of the twenty-one cases only five occurred in birds, of which only one hemorrhage was in the shape to which the term infarction is best applied. There have been, as one might expect, a few cases of infected infarction, with abscess. It is perhaps worth noting that no case of hemorrhagic cyst or inspissated coagulum has been seen. Only one case of rupture is recorded secondary to acute splenitis during an acute septicemia.
INFLAMMATIONS.
It has been the practice at this laboratory to classify splenitis in three ways, (1) acute diffuse splenitis—general congestion with perhaps small hemorrhages, swelling but retention of general architecture and with no undue prominence of the follicles; (2) follicular hyperplasia— where this is the prominent gross and minute finding, the pulp being less pronouncedly involved; (3) acute splenic tumor—where the organ is greatly enlarged but with loss of the usual markings. Perhaps this separation is not warranted upon a strict etiological basis, and yet as we shall see it holds true fairly well in the toxic and infectious lesions. Moreover, from the following list it is evident how the various orders call upon the splenic tissue in disease.
TABLE 7. _This Shows the Percentage of Various Forms of Splenitis in the Animals Coming to Autopsy._ ═════════════════╤═════════════════╤═════════════════╤═════════════════ │ Acute Diffuse │ Follicular │ Acute Splenic │ Splenitis. Per │ Splenitis. Per │Tumor. Per cent. │ cent. │ cent. │ ─────────────────┼─────────────────┼─────────────────┼───────────────── Carnivora │ 7.│ 3.│ 1.3 Primates │ 2.5│ 4.9│ 2. Ungulata │ 2.4│ .3│ 1.2 Rodentia │ 2.6│ 4.7│ 1. Marsupialia │ 9.2│ 3.│ 3.7 Pinnipedia │ _33._│ │ Proboscidea. │ _33._│ │ Edentata │ _12.5_│ │ _6.2_ │ │ │ Passeres │ 3.│ 3.│ 3.8 Psittaci │ 6.5│ 2.3│ 4.1 Anseres │ 5.2│ 7.2│ 5.2 Herodiones │ _1._│ _6._│ _2._ Galli │ 2.6│ 1.5│ 4.7 Struthiones │ _10._│ _10._│ _1._ Accipitres │ 7.5│ 3.7│ 1.6 Gaviæ │ │ │ _5._ Picariæ │ _4._│ │ _1.3_ Striges │ 6.8│ 3.4│ Fulicariæ │ _3._│ 6.│ Steganopodes │ │ _10._│ Columbæ │ .7│ .7│ ─────────────────┴─────────────────┴─────────────────┴───────────────── For the meaning of italics see foot note Table 1.
The points to draw from this chart are first the greater variety of lesions seen in the birds, which apparently make greater use of the organ in defence, and the preponderance of acute diffuse hyperplasias in mammals. It is noteworthy that the Primates and Marsupialia show more of the acute hypertrophy of the spleen going under the name of tumor. It would be interesting and valuable to be able to discover exactly what determines and constitutes the conditions usually termed hyperplasia and inflammation of the spleen and an attempt was made in this direction by tabulating the data from Table 7 in terms of each diagnosis, classifying these latter also as infectious and toxic. The results of this effort are not conclusive, and while they permit of some discussion of the lesions, do not allow finished conclusions. The figures obtained by study are not illuminating. One can state, however, that in infections, either specific or not specific, more elements of the spleen were engaged in the process than when the condition did not resemble a communicable disease, but might be called toxic. Under the former condition the diagnosis of splenitis or acute tumor predominated, while under the latter follicular hyperplasia is more often recorded. Anatomical alterations in these two groups are described in the definition given in a previous paragraph and deserve no special discussion except in so far as they concern the changes in the avian splenic tumor when under magnification.
Microscopically there is a total loss of the relations in the acute splenic tumor of birds, the chords and follicles being replaced by a rather regularly arranged mass of small and large mononuclears, granular cells of the circulating types and red blood cells; pigment always seems increased. Endothelial cells do not take part in the general mass of the organ but along lymph and blood vessels their bulk and number are increased so that if the packing be not too dense one may find double lines of these cells passing through the hyperplastic tissue. There is, however, a group of seven cases (six birds) to which the term endothelial hyperplasia in the spleen has been applied. All of them show an unusual prominence of the vascular linings and of the follicular centres and perivascular areas; besides this there is a moderate general hyperplasia. An examination of the history and autopsy results in the birds indicated that they had all suffered with some rather protracted intoxication and showed a moderate anemia (four of the spleens were well pigmented).
The more chronic changes of this organ, be they moderate or of a grade to which one must apply the term fibrosis, are rather uncommon when one considers the number of animals with prolonged infection, anemia, skeletal diseases and hepatic cirrhoses; these are the conditions that take a prominent place in the associated pathology and history. There is no essential difference in the organ throughout the animal kingdom, and one may find as far down as the struthious birds analogies to the processes of domestic and human animals.
SPECIAL SUBJECTS—AMYLOID.
Amyloid changes in the spleen have occurred in the following orders: Primates, Carnivora, Rodentia, Marsupialia, Passeres, Galli, Gaviæ, and Anseres, fourteen cases in all. This infiltration is usually ascribed to long continued suppuration or chronic infection, every one admitting, however, that once in a great while a case is seen wherein no cause can be discovered. In this laboratory we have a high percentage of cases without adequate accompanying pathology so that we have called six of the above cases primary or idiopathic. The gross appearance of the spleen is in all these cases that of an enlarged, firm, homogeneous body without the sago spots usually described for this change. Microscopically the infiltration occurs first in the vessel walls, thence spreading to the sinus walls and reticulum. Joest in discussing this infiltration[19], states that it is comparatively rare among the domestic animals, where it may appear under the usual conditions or as a primary affection; it seems at times to follow unsuitable feeding. According to this author, the “sago” type is more common than the “bacony;” this has not been our experience. The most conspicuous example is given here.
European Badger (_Meles meles_) Adult ♀ . Gradual failure for two weeks.
DIAGNOSIS.—Amyloidosis. Chronic parenchymatous nephritis. Emphysema of lungs.
Muscles atrophic; fat scanty. Heart is dilated and muscle is red- brown. Aorta is jaundiced and there is a small patch of atheroma near the anterior leaflet of aortic valve and about 5 mm. above it. Abdomen contains a slight amount of clear fluid, no adhesions. Liver is normal in size, smooth surface, sharp edges, firm consistency, yellow color. The section surface is glistening, smooth and moist. The spleen is very hard, greatly enlarged (25 × 6 × 2 cm.) and lies across the abdomen over the intestines. It is pale red and very bacony. In iodin the tissue stains a mahogany brown. The kidney is normal in size. (5½ x 3 cm.). The capsule is smooth and strips easily leaving a smooth, yellow surface. Organ is firm. The section surface is glistening, has a relatively narrowed cortex and relatively wide medulla. The glomeruli are barely visible but stain a mahogany brown in iodin. The adrenals are 12 × 10 × 4 mm. The cortex is wide, dull yellow and regular. The zone beneath fades into the cortex although rather abruptly. The centre of both glands is occupied by an irregular pale yellow, sharply outlined nodule suggestive of solid medulla, tubercle or tumor. The zone between cortex and this is gray, irregular and firm. This is practically a normal figuration. The stomach is empty, mucosa apparently normal. Intestines were not opened but serosa seems normal; when opened after Kaiserling fixation they seem normal. The pancreas is normal in size, firm and pale. Lymphatics of the mesentery are slightly enlarged, soft, homogeneous pale yellow.
HISTOLOGICAL NOTES.—Lung seems somewhat atrophic and there are some vesicular ruptures. One small patch of amyloid found in blood vessel wall. Liver shows slight capillary congestion and granularity of parenchyma. There is a marked blood vessel amyloid deposit not only in interlobular spaces but in intralobular capillaries. Spleen, no trace of splenic tissue recognizable in section. It is composed of more or less eosin-staining material surrounding single, or small collections of round or plasma cells. Kidney shows marked amyloidosis of glomeruli and slight deposit in blood vessel walls and in the increased connective tissue. There is a general moderate fibrosis; irregular tubules; low epithelium and hyaline casts. Heart muscle fibres are small and stain deeply. No amyloid in section. No pigmentation although section is suggestive of brown atrophy. Adrenal is practically negative. There seems to be slightly more connective tissue than normal but parenchyma may be considered normal. At one place in the cortex there are some structures of deep layer included in vesicular layer. This seems like a structural malformation.
NECROSES.
Focal necroses of the spleen affecting chiefly follicular centres but also chords, are not at all uncommon in avian spleens, especially where parasitism occurs, not only with hemic protozoa and embryos, but also with intestinal or visceral nematodes and trematodes.
SPLEEN IN ANEMIA.
The spleen in the anemias shows much less definite change than one would expect. In the secondary form of anemia among mammals one finds a slight excess of pigmentation and an occasional fibrosis but often the size of the organ is recorded as normal. When the impoverished blood seems secondary to skeletal degenerations there is a diffuse or follicular enlargement. In the birds, on the other hand, there is nearly always some grade of enlargement which is due in the well studied examples to a richness of blood cells. There may be a slight increase in follicles, but these bodies are usually small and solid. In two instances a prominence of large endothelial cells was discovered. Pigment is seldom increased, but it may be very excessive.
In the primary anemias little more than the above is to be found. Fibrosis is more evident and perhaps pigmentation less so, but the variations are more of degree than kind. The spleen in leucemia can only be discussed upon the case already reported (_q. v._).
[Illustration:
FIG. 7.—EUROPEAN BADGER (MELES MELES). PRIMARY AMYLOIDOSIS. THE ENORMOUSLY ENLARGED SPLEEN IS SEEN LYING ACROSS THE STOMACH BELOW THE LIVER, WHICH ORGAN IS EXCEEDED IN SIZE BY IT. ]
SPLEEN IN HEPATIC FIBROSES.
The fibroses of the liver are not infrequently associated with some enlargement of the organ under discussion. At this laboratory hepatic cirrhoses are divided into Portal, Biliary, Fatty, Perilobular and Vascular. By a study of the spleens in these cases a few facts have been obtained. In mammalian portal cirrhoses there is usually a very moderate but definite increase in the size of the spleen due to connective tissue increase in the trabeculæ and reticulum, with very small compact follicles. Among the birds the organ seldom shows more that a moderate congestion and diffuse hyperplasia. In the mammalian biliary cirrhoses there is almost without exception a definite enlargement due to fibrosis and follicular hyperplasia. Among the birds the process is very far from uniform, there being just as often no change, as a congestion and hyperplasia, or as a mild fibrosis; it is notable, however, that pigmentation is commonly met in this class. No noteworthy change is met with in the spleen of fatty hepatic cirrhoses. We have no record of cyanotic induration of the spleen accompanying a similar condition in the liver. When the condition of perilobular hepatic fibrosis has been met a distinct increase of the splenic pigment is usually found. In reviewing the facts in this paragraph one is forced to the conclusion that, with the exception of the frank infective cases, there is no definite relation of the splenic changes to those in hepatic cirrhosis, a fact made perhaps the more significant in view of the idea held in some quarters that the primary change in this pathological process occurs in the spleen.
PERISPLENITIS.
Perisplenitis of an acute or fibrosing variety as a part of peritonitis or as the result of an injury to the splenic region, has been encountered on numerous occasions and offers nothing worthy of comment, but the so-called “sugar-icing” spleen, associated with perihepatitis and general peritoneal thickening, and with an obscure relation to tuberculosis has not been seen. As we shall learn later peritoneal or massive intestinal tuberculosis is not common in the lower animals. A diffuse fibrous thickening of a pearl gray glistening appearance, has occurred in five monkeys harboring the Filaria gracilis in the peritoneum.
TUBERCULOSIS.
In tuberculosis of this organ the capsule is almost invariably thickened over the nodules, but not over the whole organ and rarely in the diffuse variety. There is almost always, however, in this prolonged infectious disease some reaction on the part of the spleen, particularly when several other viscera are involved. In such cases a low grade of general hyperplasia and fibrous tissue increase is found. This is especially true in the Primates and Carnivora in long continued pulmonary tuberculosis, and it is in this form that one does not often see tuberculous lesions proper in the spleen itself. Tuberculosis of the spleen is not very common in adult human beings and domesticated animals, while in the young it is seen in a fairly high percentage of cases. In the wild animals this organ seems much more susceptible to the settling of tubercle bacilli as will be attested by the facts to be cited, and yet there are some conspicuous exceptions to this statement. Just why certain groups, or orders should show splenic tuberculosis very frequently while others fail to do so is far from clear.
The appearance of the lesion is fairly comparable throughout the animal kingdom, variations among the Aves being chiefly in the more frequent occurrence of the diffuse tuberculous splenitis. Miliary, caseous and conglomerate masses occur separately or together and without very distinct relation to other pathological involvements.
The relative incidence of tuberculosis in the spleen is set forth in the section devoted to this infection, but may be mentioned here in a general way. The organ is about equally susceptible to the disease in mammals and birds according to the figures, but the high percentage for the former is due to the frequency with which tuberculosis is met in the Primates. With this order deducted there is no doubt that the avian spleen has a greater vulnerability for the tubercle bacillus than has the mammalian organ. Rodentia as a mammalian order stand next to the Primates, whereas the Carnivora and Ungulata relatively seldom show splenic tuberculosis. Among the Aves one finds that Columbæ, Galli and Accipitres have the highest splenic susceptibility, but beyond this one hardly dare venture because of the irregularity in the number of specimens seen at autopsy. Suffice it to say that a greater number of cases of tuberculosis are seen in the spleen of the class for which the intestinal origin of tuberculosis appears most important.
In the cases of actinomycosis and its congeners, such as the Kangaroo maxillary mycosis, which we have seen at the Garden, no specific changes have been seen in the spleen, unless a single or double nodule of the same variety as the original focus may be considered specific. Such was found in two cases, one a tapir with low grade inactive actinomycosis, the other a kangaroo with maxillary streptothricosis. Two deer came to autopsy with a gross picture suggestive of anthrax; no bacilli could be found in the semifluid spleen, but a member of the hemorrhagic septicemia group was found. The latter group of infections has been fairly well represented, although not in epizoötic form, and the almost invariable splenic change has been that already discussed as diffuse splenitis. Three secondary tumors are recorded, two cancers and one renal adenoma.
SECTION VI THE RESPIRATORY SYSTEM AND ITS RELATED STRUCTURES
It is customary to divide the descriptions of normal and diseased conditions of the upper entrance to the body into respiratory and alimentary parts, the nose, nasopharynx and larynx belonging to the former, the mouth, buccal cavity and pharynx to the latter. As a matter of fact they can for most purposes be considered as the structures contained in the anterior head and furthermore their pathological states are more often followed by extensions into or implications of the respiratory organs proper than of the alimentary tract. From a comparative standpoint the incidence of specific infectious diseases and of the involvement of accessory nasal sinuses present the most interesting subjects. There are several infections, believed to be specific, observed among domestic mammals and birds but their actual individuality has hardly been unexceptionally proved. This refers to the communicable rhinitis of cows, pigs, rabbits, and birds, especially parrots, the follicular catarrh of horses, and croupous nasopharyngitis, all of which have been ascribed to a particular virus, without finished evidence in many instances. Some of these diagnoses doubtless cover or are confused with the early symptoms and signs of the disease of protean manifestations, distemper, and indeed the Bact. septicus and relatives of the bird cholera organisms are reported as being responsible for them. No intention of excluding well recognized entities like bird diphtheria, foot-and-mouth disease or influenza, exists. I shall refer below to small groups of epizoötics which do not conform strictly with word pictures drawn by Hutyra and Marek, Moore, or Ward and Gallagher.
RHINITIS, SINUSITIS.
The nature of inflammations of the nasopharynx suggests at once that there may be some anatomical reason for their distribution and character. A general review of the anatomy of the mammalian and avian nasopharynx reveals the relatively greater space in the former, especially in the passage from the nose to the pharynx, and emphasizes the exposure of the opening of the upper larynx in the bird, lying as it does in the posterior part of the tongue and surrounded by the constrictores glottidis. A dissection of the accessory nasal sinuses exposes the relatively large size of these spaces in the lower mammals, and the capacious openings into the nasal cavities.[20] In the Primates and Lemures the anatomy more closely resembles that of man, the sinuses being relatively smaller and the communicating passages narrower. In the bird on the other hand, while the sinuses may be extensive in some they are usually small, yet in all the communication with the turbinate area is by a narrower slit or tortuous canal, frequently, as in Galli, running from below upward into the maxillary sinuses. The extent of the turbinate and the richness in mucosa is probably greater in all mammals than in birds; certainly this seems true of Carnivora and Ungulata _versus_ Accipitres and Galli.
If the seriousness of a rhinitis be dependent upon the extent of involvement of the sinuses and the blocking up of their outlets it would be expected that the variety of animal having the smallest drainage channels would show the greatest evidence of these diseases. Our records would indicate that 32 birds (.96 per cent. of the autopsies upon Aves) had rhinitis whereas only 7 mammals (.39 per cent. of autopsies on this class) presented the condition. Extension to the sinuses occurred in only one-third of each of these figures, a complication which in turn produced generalized infection more often in mammals than in birds as 4 is to 3. These figures are perhaps too small for conclusions but it would seem that rhinitis occurs more often in birds with their small sinuses and channels while sinusitis and general infection occur more often in mammals with their large sinuses and extensive turbinate apparatus. The most conspicuous orders represented are, in line of numbers Anseres 12, Psittaci 7, Accipitres 5, Carnivora 3. Nine of the twelve waterfowl were part of an epizoötic which will be discussed under specific diseases.
Bacteriologically the mammalian cases that have been worked out were due to _Streptococcus pyogenes_ in several instances, including the generalized cases, and to a mixture of streptococci, golden staphylococci and members of the colon-aerogenes group. In one case in a tapir a member of the B. septicus group was found. Moulds were discovered in three avian cases and filaria in one. No pentastomum or œstrus has been discovered. In thirteen instances the lungs have been involved, apparently secondary to the nasopharyngeal disease.
There have been two small outbreaks of an acute nonspecific infection— that is not suggestive of cholera, psittacosis or infectious enteritis— among the parrots in which during a short time 4 and 6 parrots died with nasopharyngosinusitis as the prominent lesion. One outbreak was studied bacteriologically without definite result. There was no uniform internal pathology unless, in one outbreak, congestion of the cerebellum may be mentioned. Fowl diphtheria and its associated condition from which a satisfactory separation has not been accomplished, epithelioma contagiosum, has happily given us little concern, so that it is not possible to record any instructive facts upon its cause or differential diagnosis. There was recorded in the 1911 Report of the Society the occurrence of two fatal cases in cassowaries from which it was possible to isolate the B. columbarum and one bird with the same clinical appearances whose recovery seemed to be due to the use of human diphtheria antitoxin. In light of more information and consideration of the accepted variability of this disease, it is possible that this bird may have recovered without the injections or with the use of normal serum. Nowadays it is possible to obtain antiroup serum which is stated by Blair of New York to be efficacious. The disease has been observed in a wild turkey and an Abyssinian Ground Hornbill, beside the two struthious birds mentioned above.
MYCOSIS.
Mycotic disease of the nasopharynx seldom restricts itself to this cavity, usually extending by continuity to the esophagus, or by inspiration to the lungs whence it spreads to the air sacs. This condition of the upper passages has occurred here only in Psittaci and Accipitres although it is reported by veterinarians as occurring in Anseres and Struthiones. In the first order four birds were affected, two showing extension to the esophagus and a like number having pulmonary and serous membrane involvement. These cases were all due to aspergillus whereas those next to be mentioned were caused by an oidium close to the “albicans” variety. In four Mississippi kites the prominent changes were found in the pharynx and esophagus down as far as the proventricle with only a few rather trifling lesions in the nasal area. Infiltrative and necrotizing processes characterized the action of the oidium while that exerted by the aspergillus was more superficial and extensive. In one case of a parrot the whole nasal cavity was completely filled with a yellow gray exudate whereas the esophageal wall of the kites was thoroughly infiltrated by a gray-brown, friable, necrotic mass. Attempts at treatment were made in the case of the latter, using potassium chlorate and saline solution on cotton swabs. The result was entirely negative and the applications seemed to have no effect upon the course of the infection.
There are on our records in addition to the above, several cases of necrotizing processes about the head seeming to emanate from wounds to the mucosa by foreign bodies, by decomposition of pieces of food in crevices or by damage by masses too large to be swallowed. In the few instances where we have tried bacteriology, no definite result has been obtained unless the frequent occurrence of organisms bearing a resemblance to Bact. necrophorus be important. This organism however may be found in many necrotic processes in animals; I do not look upon it as specific in the locations just cited.
Mammals as a class do not present many inflammatory conditions around the anterior head, aside from the specific diseases like distemper (?), actinomycosis, Kangaroo disease and the like. Monkeys occasionally have acute coryza, which may indeed seem transmissible to others but it seldom leads to any serious consequences and is untreated, except by segregation. Tuberculous lesions are not recorded. There has been no glossitis aside from lesions involving the pharynx. The tonsils have been discussed under the lymphatic apparatus and it only need be repeated here that inflammation and hypertrophy of these organs are exceedingly rare. Specific or individual diseases of the salivary glands are also rare although these organs may be involved by extension. This general region is not often affected with tumor, unless the jaw be included which bone is the seat of several tumors in antelopes and opossums. Aside from these we have seen an epithelioma of the tongue in a black bear (_Ursus americanus_).
LARYNX.
The larynx is an organ of fairly uniform construction through the mammalian orders but is conspicuously different in the Aves where it is double. The upper end of the trachea in the latter class is surmounted by a cartilaginous box lying beneath the root of the tongue through which an anteroposterior slit-like opening forms the glottis; there is no epiglottis. This is only an air passage, the voice being made in the syrinx or lower box which lies at the bifurcation of the trachea. The structure of the upper box is quite simple with its lateral plates controlled by the glossal muscles and two external retractors but the syrinx is very complicated and variable in the different orders and even in the same family. It possesses an internal and external set of muscles and in some birds can be opened at one point to permit air to pass to the cervical or thoracic air sacs. Detailed discussion of its anatomy is hardly profitable since there is nothing peculiar about its diseases. On one occasion only have we seen distinct pathological change—what was probably an extension of mould disease from it to the cervical air sac. It is involved in true tracheitis and bronchitis but even these are rare in birds.
The larynx on the other hand is constantly reddened in cases of pharyngitis and may be the seat of mould colonies. Edema of this structure is, however, not very common, it being recorded but twice in birds in association with nearby inflammation and five times in mammals; in the latter cases three were of acute infectious nature, one was a tumor and the other osteomalacia. It is common to find the laryngeal and tracheal mucosa swollen and wet in chronic bone degenerations without the condition being severe enough to call it edema.
LARYNGITIS.
Acute laryngitis of active catarrhal or purulent nature has been met five times in mammals and twice in birds while more chronic lesions have occurred only in the former, four times. Tuberculous laryngitis has been observed in a cockatoo and a lemur; they are interesting enough to cite. There are no cases recorded among monkeys despite the large number dying from the disease; this implies of course that no suspicion of its existence was had at postmortem but perhaps some would have been detected had every larynx been subjected to microscopic section. A citron-crested cockatoo was found when posted to have general miliary tuberculosis. The bright red rim of the glottis attracted attention and upon slitting open the organ, pinhead size, sharply outlined yellow tubercles were found on both sides. A black and white lemur was killed because of a positive tuberculin test. He was in good condition and exhibited as his only lesions retropharyngeal lymph nodes with precaseous miliary nodules and small miliary tubercles on the epiglottis, true and false vocal chords and in the mucosa of the main ventricle, each lesion being surrounded by a narrow sharply injected zone. This seems like a recent double implantation since the retropharyngeal glands probably do not drain toward or from the larynx. The larynx has been the seat of only one tumor, a squamous cell cancer in an Azara’s agouti. The tumor caused ulceration and edema of the whole mucosa sufficient to produce fatal asphyxia.
The trachea is of relatively little comparative or pathological interest aside from its inflammations which however are so closely associated with bronchitis that they will be included under that heading. Perhaps the most important condition of this tube is its infestation with _Syngamus trachealis_ since this leads to inflammations not only of the related mucosa but predisposes to pulmonary infection. The occurrence in the Galli is well known but perhaps it is not so well recognized that this worm occurs also in crows (Passeres) and swans and geese (Anseres). For the diagnosis of this condition it is customarily stated that a frothy mucus in the mouth is very suggestive; this is true in the cases seen here but in addition a mucopurulent stomatitis is exceedingly common and when the two are combined the picture is almost confirmatory. Although worms are credited with considerable weight in the production of pneumonia in Ungulata, they have only been seen once within the tracheal tube.
THE BRONCHI.
The bronchi will be discussed as a separate part of the respiratory system in so far as possible since they present a very decided difference in anatomy between mammals and birds and because the incidence of their disease is other than will be found for the lungs. However, distinction has been made between changes in the grosser tubes and those in the finer bronchioles, especially because capillary bronchitis so-called is really a pneumonitis in which the mucosa of the larger passages need not participate. The mammalian tubes are not really greatly different in their construction, passing through ever smaller branchings which give an increasing square area of tube capacity and more extensive mucous surface. The avian main bronchus breaks up very shortly after entering the lung into a varying number of spaces lined with low epithelium lying upon a fibrous support and without cartilage. These spaces then open into secondary air spaces of a size visible to the naked eye which are in turn surrounded by microscopic alveoli. The largest spaces, first mentioned, continue to grow smaller toward the lower part of the lung where they usually communicate with one or other of the various ostia of air sacs. Bronchial diseases in birds must therefore be limited at the place where the bronchi lose the cartilaginous rings since below this the surface functionates as pulmonary tissue.
BRONCHITIS.
The accompanying list, Table 8, will show the distribution of bronchitis not accompanying pneumonia or due to mycosis. It is striking that carnivorous animals are more prone to bronchitis than any other order (the struthious birds are too few to be important). There is a very decided preponderance of mammalian cases over avian, there being not only more cases but proportionately more orders affected. The character of lesions in the mammals is nearly always catarrhopurulent or freely purulent while ulcerative changes are not uncommon. Peribronchial infiltrates are seldom found without some evidence of pneumonia; nor is it common to meet the pale lines extending from bronchi between the lobules, such as are seen in human streptococcal disease. Avian bronchitis is usually hemorrhagic or catarrhal and with exceeding rarity becoming purulent; when this occurs the cause is frequently found to be tuberculosis or mycosis. Inflammation of the larger passages is nearly always accompanied by pulmonary congestion, a serious condition in birds as will be seen later. A few of these cases have been studied bacteriologically with no definite result, nor have these cases occurred in such groups that an epizoötic was suggested. Bact. avisepticum, Bact. canisepticum, Bact. coli, Bact. aerogenes mucosum, and Ps. pyocyaneus, Streptococcus hemolyticus and non-hemolyticus and staphylococci have been found.
TABLE 8. _Showing the Percentage Incidence of Bronchitis and of Parasites in the Autopsies upon the Various Orders._ ════════════╤═══════════════════╤═══════════════════╤═══════════════════ Orders │ Simple Bronchitis │ Verminous │Inactive Parasites │ │ Bronchitis and │of Lung (Encysted) │ │ Pneumonitis │ &c. ────────────┼─────────┬─────────┼─────────┬─────────┼─────────┬───────── „ │ Cases │Per cent.│ Cases │Per cent.│ Cases │Per cent. ────────────┼─────────┼─────────┼─────────┼─────────┼─────────┼───────── Primates │ 7│ 1.4│ 3│ .6│ 5│ 1. Lemures │ │ │ │ │ 1│ 1.2 Carnivora │ 14│ 2.9│ 8│ 1.6│ 8│ 1.6 Insectivora │ │ │ │ │ │ Chiroptera │ │ │ │ │ │ Rodentia │ │ │ 2│ 1.│ │ Ungulata │ 5│ 1.3│ 2│ .5│ 10│ 2.7 Proboscidea │ │ │ │ │ │ Hyracoidea │ │ │ │ │ │ Edentata │ │ │ │ │ 2│ _12.5_ Marsupialia │ 3│ 1.7│ 2│ 1.1│ 3│ 1.7 Monotremata │ │ │ │ │ │ │ │ │ │ │ │ Passeres │ 4│ .29│ 7│ .5│ 2│ .16 Picariæ │ │ │ │ │ │ Striges │ │ │ │ │ │ Psittaci │ 4│ .58│ │ │ │ Accipitres │ 1│ .5│ │ │ │ Columbæ │ │ │ │ │ │ Galli │ │ │ 1│ .3│ │ Hemipodii │ │ │ │ │ │ Fulicariæ │ │ │ │ │ │ Alectorides │ │ │ │ │ │ Limicolæ │ │ │ │ │ │ Gaviæ │ │ │ │ │ │ Impennes │ │ │ │ │ │ Steganopodes│ │ │ │ │ │ Herodiones │ 1│ 1.│ │ │ 1│ 1. Odontoglossæ│ │ │ │ │ │ Palamedes │ │ │ │ │ │ Anseres │ 2│ .67│ 3│ 1.│ │ Struthiones │ 1│ _3.3_│ │ │ │ ────────────┴─────────┴─────────┴─────────┴─────────┴─────────┴───────── For meaning of italics see footnote Table 1.
A review of the active verminous lesions of the bronchi and the pneumonitis to which parasites lead, shows again the highest number among the Carnivora, with negligible percentages among the Aves. The forms concerned are, when determined, ascarides, strongylus, hepaticola, fasciolopsis, cytoleichus, pneumonyssus and paragonimus; these will be discussed later. The lesions in the bronchi are mucocatarrhal or hypertrophic; occasionally actual ulcerations are seen. What is more important however is the peribronchitis leading to interstitial pneumonitis and to bronchiectasis of the smaller bronchi, or to areas of atelectasis by total occlusion of some small air passage. This pathology is fairly well recognized among veterinary pathologists but there are two points which seem worthy of special emphasis, namely, the relative mildness of the changes in the larger bronchi and the importance of the worms as causes of pneumonia. In regard to the first it can be pointed out that the trachea and its branches need not be altered at all while the middle sized bronchi present a mottling of small recent congestion with pigmentations from old hemorrhages, together with slight unevennesses of the surface. Small bronchi on the other hand are the seat of ulcerative internal processes and quite marked peribronchitis, as indicated by round and connected tissue nuclei or perhaps polynuclear increase under active acute inflammation; it is in the latter case that acute pneumonitis is present.
To what extent do the parasites predispose to pneumonia? Compare for this purpose the two columns of Table 8 showing active and inactive pulmonary parasitism. In Rodentia and Galli alone do we note that active parasitism is effective, there being no passive cases. In all the other orders, animal invaders of the lung are more often encountered as quiescent or encapsulated bodies, therefore as findings incidental to the autopsy and perhaps not concerned in the cause of death. In Ungulata the inactive parasitisms are five times as frequent as the active inflammatory lesions. It might be added that the list is made up of cases wherein we saw parasites whether determined or not, an explanation of the apparently small number of cases; there were many more in which such invaders were suspected but not found and therefore excluded.
BRONCHIECTASIS.
Bronchiectasis affecting the smallest tubes, or bronchiolectasis, is not at all uncommon in verminous pneumonitis and is explained as due to the degeneration of the wall, the surrounding progressive ulceration, to accumulation of inspired air and its retention by the obstruction. There is described a generalized bronchiolectasis, chiefly in young human beings, due to a destructive bronchiolitis; this has not been seen.
Non-verminous bronchiectasis of the middle sized bronchi such as is seen in human chronic bronchitis, simple or tuberculous, is quite uncommon. Widening of the bronchial lumen may be divided, as I see its pathogenesis, into (a) that due to congenital weakness of the walls, (b) that due to obstruction permitting air to pass into but not out of a bronchus because of a ball-valve obstruction or weakness of expiratory power, (c) that due to external pressure by tumors or distortion by fibrous tissue either within the lung or pleura and (d) that due to inflammatory weakening of walls, augmented by loss of supporting pulmonary tension, accummulation of secretion and the dilating effect of inspiration preparatory to and incidental to coughing. How important the last three auxiliary factors may be in the cases explicable under a, b, c, can easily be speculated upon and may vary in different cases.
Bronchiectasis is reasonably common with pulmonary diseases of man, particularly of chronic character, but is certainly not frequent among animals. Under the first group (a) we can record one case, a Siberian tiger which died of enteritis and its complications to which were added a mild inactive bronchitis and a bronchiectasis of diffuse distribution. The lungs were irregular in shape, dull, gray-red in color and gave a variable boggy and vesicular sensation to the fingers. On opening the lung, dilatations of the bronchi were found, affecting chiefly the larger secondaries but apparently not the bronchioles. Parasites were not found nor were inflammatory reactions apparently adequate to explain the distentions, so that we looked upon this case as congenital. Cases coming under the headings b and c are not recorded. Inflammation almost certainly represents the most important single factor in the pathogenesis of this lesion and could be demonstrated in two cases, a Clouded Leopard (_Felis nebulosa_) and a Red River Hog (_Potamochærus porcus_). While I feel that parasites probably laid the foundation for the dilatations in these cases, none were found after, in one case at least, a very thorough search, although in the second animal a single cyst of _Cysticercus tenuicollis_ was found in the peritoneum. In both animals there was a low grade interstitial pneumonitis and peribronchitis with dilatations of the middle sized and end bronchi, these being supplied with thick walls but containing very scanty secretion.
We have on record chronic ulcerative pulmonary tuberculosis in six primates, two carnivores and nine ungulates. It is highly probable that among this number some cases of ulcerative bronchiectasis occurred but if so they were not conspicuous enough to mention in the diagnosis and in only two protocols do I find a discussion thereof, once in a monkey and once in a carnivore. All the cases of our records were diffuse ectasias, fusiform, or irregular and none of the distinct saccular variety.
From the foregoing facts it would seem that in human cases more weight should be laid to the effect of the dilating power of coughing and its preparatory exertions. While I am aware that the comparative incidence of human and lower animal bronchiectasis cannot be based upon the meager figures at our command, these dilatations certainly can be expected in a general autopsy service more in man than in lower animals. Chronic bronchitis is relatively rare, aside from the verminous varieties. I have seen little retained exudate in the bronchi, probably because quadrupeds seem with ease to raise and swallow the secretions. Nor do animals give vent to paroxysms of coughing such as the human being feels forced to do. Suggestive deductions from these points are that inflammation is the principal factor in acquired bronchiectasis and that the retention of secretion with violent inspiratory efforts are potent in man for the dilatation of the tubes.
THE LUNGS.
The essential respiratory organ of the animal body, the lung, is all through this kingdom a structure intended to expose the blood to free or combined atmosphere in order to permit gaseous interchange, therefore being arranged so that there is a close apposition of the two factors, separated only by such cells and membranes as may be necessary to protect the circulation; perhaps these anatomical elements possess at the same time some vital force to further the exchange of useful and useless matter. In the two classes under discussion there is no difference whatsoever in the primary factors of respiration albeit some variations exist in reference to oxygen and carbon dioxide interchange, moisture of the air, and the physics of inspiration and expiration. The chemical variables have in our limited knowledge of comparative physiology apparently little effect upon morbid anatomy but it is probable that some pathology may be in part explained on physical grounds.
The mammalian respiratory box is a relatively elastic affair, but collapsed at the end of expiration which is largely a passive or recoil process. The avian thorax is believed to be normally a tensely distended space from which air is expelled by pressure of the pectoral contraction upon the broad sternum driving the latter back upon the air sacs which in turn drives it from the lungs. Also by this means, air is distributed through the bones and air spaces, a measure necessary in flight, especially in a head wind when tracheal inspiration is said to be suspended at times. The communications of the lungs, air sacs and bones make it possible for birds to breathe internally when the trachea is closed and externally as well if a bone be opened. The balance of air pressure in the lungs and related spaces is dependent upon the patency of the ostia communicating between the bronchial ends and the air sacs, from which the bony cavities obtain their supply. Should all these be closed there is first a standstill of current and a limitation of the respiration of the lungs. Fortunately it is extremely rare that this occurs for it is obvious that it is incompatible with flight, and with life indeed. The principal effect upon the lungs of obstruction to the passages seems to be expressed in congestion but in how far this is due actually to the closure of foramina and how far to the cause of obstruction is sometimes difficult to evaluate. It should be remembered that the air sacs are usually looked upon as mucous surfaces continuous with the bronchial wall, there being a deep layer to each membrane possibly continuous with the serous membranes. In mould disease of the lungs there is very commonly a colony lying in the ostium supplying the anterior, lateral and posterolateral cavities.
The lungs in birds are not free as in mammals, being fitted into the troughs made by the anterior ridges of the ribs, to the serous covering of which they are lightly attached by delicate fibres running between the two. This more or less definite fixation, together with the pressure of the air in the sacs give the free play of the lungs a limited excursion. They are naturally very elastic by reason of a good supply of elastic fibers and large air spaces, a condition aided by their attachments to the supports of the diaphragm and to the insertions of the air sac walls. Notwithstanding this elasticity and the great capacity of the organ for blood, it seems as if congestion of the lungs is a very serious matter, since from the foregoing review of anatomy, accommodation of excess blood and any consolidation must be difficult. As a matter of fact the mere excess of blood known as active congestion seems able to kill small varieties.
CONGESTION OF LUNGS.
Birds of flight seem to have little resistance to this condition and often it is the only diagnosis one can make at autopsy. The causes of this condition include exposure, dust, gorging (?), indigestion, enteritis and infection in birds while in mammals acute gastrointestinal disease stands out as the most prominent accompaniment. To what extent dust and exposure operate I do not see, although they are frequently mentioned as causes. The overfilling of the crop, esophagus and proventricle, the turgescence incident to gastric indigestion or the pressure of foreign bodies in large amount are supposed to operate by exerting pressure on the anterolateral air sacs with closure of their ostia and also by right lateral torsion of the heart with twisting of the very delicate pulmonary veins.
I have sought to show that protozoa or embryo nematodes in the blood might embarrass the lungs to a state of congestion, a thought suggested by some findings in the London Gardens, but only about ten per cent. of our cases of hemic parasitism are accompanied by it.
The incidence of congestion of the lungs not due to stasis as from cardiac diseases, is 2.4 per cent. in mammalian autopsies, in only 7 per cent. of which figure did it represent the principal morbid anatomy, whereas in birds it occurred to the extent of 7.6 per cent. of postmortems, in 17 per cent. of which it was the sole or principal cause of death. This seems to bear out the feature of delicacy of the pulmonary vascular mechanism in these latter animals. This condition seems to be indicated by simple dyspnœa in birds, relief for which has occasionally been afforded by removal from the exhibition cages and protection separately in a warm dry room; this is partly hypothetical of course and congestion is to be looked upon as serious, particularly in passerine birds.
PNEUMONIA.
Pneumonia as a clinical disease is a relatively uncommon, although quite serious sporadic condition in animals. However accompanying the specific, more or less epizoötic diseases such as influenza, distemper and the choleras it may be a frequent and quite pronounced complicating feature of the case. Pneumonia _per se_ has exacted a reasonable toll in this Garden but unfortunately recognition being impracticable, diagnosis and treatment have not progressed. Nor has it been practicable to group our cases pathologically because of the lack of history and the difficulty of making bacteriological observations at many autopsies. Fortunately we have had practically no epizoötic pneumonias, an experience shared with other gardens judging by their published reports. Etiologically, and of course this applies to non-verminous, non-mycotic and non-tuberculous cases, the pneumococcus has stood out prominently as a cause with a few additional cases due to the streptococcus and the Bact. aerogenes mucosum group; London reports four cases in monkeys due to the Friedlander bacillus. Some time ago Doctor Weidman subjected our pneumonias to an analysis and was able to show that there is no parallelism between the seasonal incidence of pneumonia in man and animals, rather indeed that the Garden is more apt to have a greater number of cases in the summer, a sort of “closed season” for man. This I am inclined to interpret as connected with the larger number of visitors during that season. Doctor Weidman was further able to show that the only real examples of lobar fibrinous pneumonia strictly comparable to the human infection occurred in the Primates. I have uncovered one in a lemur and one in a carnivore. The pneumococcus has been far and away the greatest producer of our pneumonias, in two typed cases being of the IV variety. There will be given below a summary of the pathological types of pneumonia encountered, to be followed by some notes upon the principal gross and minute anatomy in special orders. Table 9 will show the numerical distribution of types among the orders. All the principal mammalian orders are represented while the birds seem relatively less susceptible to the disease and, except the Passeres, show a trifling incidence.
TABLE 9. _Showing the Number of Cases of the Various Forms of Pneumonia Found in Each of the Orders._ ════════════╤═════════╤═════════╤═══════╤══════╤══════════╤═══════╤═══════════ │Fibrinous│Catarrhal│ Acute │Septic│Hypostatic│Chronic│Pleurogenic │ Lobar │ │Inter- │ │ │Inter- │ │ │ │stitial│ │ │stitial│ ────────────┼─────────┼─────────┼───────┼──────┼──────────┼───────┼─────────── Primates │ 4│ 22│ 2│ 1│ 1│ 2│ 2 Lemures │ 1│ 3│ │ │ │ │ Carnivora │ 1│ 34│ │ 4│ │ 1│ Insectivora │ │ │ │ │ │ │ Chiroptera │ │ │ │ │ │ │ Rodentia │ │ 6│ │ 3│ │ │ Ungulata │ │ 14│ │ 5│ 1│ 1│ Proboscidea │ │ 1│ │ │ │ │ Hyracoidea │ │ │ │ │ │ │ Edentata │ │ 1│ │ │ │ │ Marsupialia │ │ 13│ 1│ │ 1│ │ Monotremata │ │ │ │ │ │ │ │ │ │ │ │ │ │ Passeres │ 1│ 59│ 2│ 2│ │ │ Picariæ │ │ │ │ │ │ │ 1 Striges │ │ 3│ │ │ │ │ 1 Psittaci │ 1│ 15│ │ │ │ 1│ Accipitres │ │ 1│ │ │ │ │ Columbæ │ │ 2│ │ │ │ │ Galli │ │ 2│ │ │ │ │ Hemopodii │ │ │ │ │ │ │ Fulicariæ │ │ 1│ │ │ │ │ Alectorides │ │ │ │ │ │ │ Limicolæ │ │ │ │ │ │ │ Gaviæ │ │ │ │ │ │ │ Impennes │ │ │ │ │ │ │ Steganopodes│ │ │ │ │ │ │ Herodiones │ 1│ │ │ │ │ │ Odontoglossæ│ │ │ │ │ │ │ Palamedes │ │ │ │ │ │ │ Anseres │ 1│ │ │ │ │ │ Struthiones │ │ │ │ │ │ │ ────────────┴─────────┴─────────┴───────┴──────┴──────────┴───────┴───────────
Primates present a definite group of variations from the other orders, notably in having four clear cases of lobar fibrinous pneumonia, and in certain histological findings. In reference to the lobar cases, a review of their history does not indicate that any might have been surely diagnosed by their symptoms, and only possibly by signs in one case during the stage of red hepatization; unfortunately no temperature records are at hand. In one case it was possible to see a group of alveoli with the fibrin collected in a strand which, according to classical description, passes through the septum to the adjoining alveolus.
There were two cases, a Chimpanzee (_Pan niger_) and a Galago (_Galago maholi_) with a microscopical picture suggestive of those we met in the influenza epidemic, and indeed the lung of the former resembles grossly the lung of influenza pneumonia. The spotty areas of watery purple color correspond under magnification to celluloedematous semisolid sections showing a sanguineous exudate, few polynuclear cells and many swollen epithelia. The microscopic picture of the bronchocatarrhal pneumonias shows conspicuously thickened septa decidedly wider than one is accustomed to see in human cases and apparently due more to round cell infiltration than to congestion or polynuclear increase.
Bronchopneumonia or capillary bronchitis with zones of cellular edema in the vicinity is a rather usual picture in the deaths from degenerative bone disease. It cannot be said that there is anything very peculiar about it, although a frequent note met in the autopsies describes spotty areas of hemorrhage and nearby atelectasis.
The case of lobar pneumonia found in a ring tailed lemur (_Lemur catta_) showed very delicate fibrinous reticulum and relatively few cells in the exudate, a picture apparently due in part to beginning resolution since the whole upper left lobe was in a stage of gray hepatization.
The peculiarity of the Carnivora seems to lie in the reaction of the epithelia, these cells being quite large, swollen and occasionally much vacuolated. Such a picture was most pronounced in the terminal bronchitic pneumonias in cases which might be called distemper. Many instances of pseudolobar catarrhal or bronchopneumonia are recorded but we also observed the fibrinous lobar form at the stage of red hepatization in a Texas skunk (_Mephitis mesomelas_). Concerning the orders Rodentia and Edentata no especial notes seem necessary for their inflammatory reactions are essentially like the others in that epithelial cells are much swollen and prominent.
Pneumonias of Ungulata are well known to pathology and offer in causation and microscopy little that is peculiar. It might be emphasized however that the gross appearance of the bronchocatarrhal variety closely simulates that of lobar pneumonia, therefore to be called a pseudolobar form, in that extension to various parts of a lobe seems to occur. Moreover in the bronchitic varieties associated with enteritis, with or without infectious foci in the pharynx or larynx, there may be two or even three stages of the pneumonitic process in one lung or lobe. It seems that this pseudolobar appearance occurs definitely more often in ungulates than in the other orders.
[Illustration:
FIG. 8.—NORMAL AVIAN PRIMARY AND SECONDARY ALVEOLI. NOTE THE DELICACY OF THE SEPTAL PROLONGATIONS THAT BOUND THE PRIMARY ALVEOLI, ALL OF WHICH ARE WIDELY OPEN. ]
[Illustration:
FIG. 9.—EARLY BRONCHOPNEUMONIA OF SUPERFICIAL ORIGIN. NOTE SOME LITTLE EXUDATE IN SECONDARY ALVEOLUS. WIDE SWOLLEN SEPTA AND BOTH ALVEOLI REDUCED IN SIZE. ]
Marsupialia offer two rather easily grouped classes of bronchopneumonia— one associated with enteritis and one secondary to “Kangaroo disease” of the jaw; they differ in microscopy correspondingly. The simple bronchitic and peribronchitic infiltrate and superficial exudate occurring with enteritis or with a general infection is relatively diffuse, giving in some instances the impression of an interstitial process and showing notably swollen septa; there may be fibrin but this is exceptional and scanty. When mycosis of the jaw has been the origin or occasion of the infection the picture is that of frank aspiration pneumonia, therefore more like a septic infarct. However the amount of fibrin is sometimes very great and whole alveoli will be filled with it, perhaps accompanied by red cells, polynuclears and epithelia. Epithelial cells however play a small part in the minute anatomy. Hemorrhage and edema are prominent but true abscess formation and gangrene are not. Possibly the animals die too soon for the latter to develop.
Pneumonia in Aves aside from that due to moulds is apparently much less common than among the Mammalia, one order only, the Passeres, showing an incidence comparable to the important orders of the latter class. The other orders, and this applies particularly to those of which we have an adequate number, are quite insusceptible to simple pneumonia, none of them showing over two per cent. There are listed for Aves three instances of lobar fibrinous pneumonia. These cases can be described together since in all the findings were about the same. A whole lung or goodly portion thereof was uniformly involved in a red or gray consolidation of rather fine granular character which on section study seemed to be made up of the same lesion all over, with fibrin a prominent part of the exudate. The coagula were largely within the secondary alveoli but the primaries also contained it. The microscopic section may not have represented the process at all places, and since the arrangement of fibrin is similar in definitely catarrhal lesions, these may of course have been instances of pseudolobar pneumonia.
Our data are too few to draw any conclusions as to the behavior of the various orders but one note may be permitted. The passerine birds have a great tendency to dense cellular infiltrates while parrots show more coagulative or fluid exudates.
PRODUCTION OF INSULAR PNEUMONIA IN BIRDS.
Insular consolidations in which catarrhal and infiltrative processes are prominent, the bronchopneumonias, seem to arise in two ways. One course of events apparently follows infection _via_ the bronchial mucosa, the other _via_ the blood stream and a study of the resulting lesions may help toward an understanding of the development of pneumonia in man.
When infection unquestionably has been superficial, that is _via_ the bronchus, the first thing to happen is a swelling of the septal prolongations dividing the primary alveoli and an extension of their ends farther into the secondary alveoli with the result that the inlet to the primary air sacs is narrowed and the space in the secondaries is reduced. Upon the surfaces there then develops the usual catarrhal exudate while in the deeper parts marked congestion makes its appearance. Fibrin may develop and be mixed with the cells both in the larger and smaller alveoli but it is more evident in the former. (Figs. 8, 9, 10.)
[Illustration:
FIG. 10.—LATER BRONCHOPNEUMONIA OF SUPERFICIAL ORIGIN. NOTE GREATER EXUDATE, GREATER SWELLING OF SEPTA. PRIMARY ALVEOLI PRACTICALLY ALL CLOSED. MUCH OF LUNG HAS BECOME CONSOLIDATED. ]
[Illustration:
FIG. 11.—INSULAR PNEUMONIA, BEGINNING AS CELLULAR INFILTRATION OF DEEPER PARTS OF SEPTA AND OF INTERSTITIAL TISSUE. FOUR AREAS OF DENSE AIRLESS CONSOLIDATION. ALL SECONDARY AND MANY PRIMARY ALVEOLI WIDELY OPEN. ]
The other process by which insular pneumonia develops seems to begin in the septa of the smaller alveoli and in the perivascular areas. This has been looked upon as hematogenic or pleurogenic. The first change occurs in the surroundings of the primary alveoli where there appears a richness of nuclei, of round, moderately well stained character, among which one may see a few granular and red blood cells. Soon the epithelia of adjacent alveoli increase in number and a fibrinocellular exudate appears, at first probably in the smaller sacs. However when the lesion is intensive the course of events must be rapid for the identity of a group of primary alveoli is soon lost and the exudate may extend to the larger air space. (Fig. 11) In severe or late cases a decision as to the course of origin is often impossible. The most instructive point of this part of the study is the closing of primary alveoli by the swelling of their septal ends and the early occlusion of the secondary alveolus by a catarrhofibrinous or even pus-like material. It is quite possible that a similar course of events transpires in the pathogenesis of human pneumonia, the superficial avian form being comparable to the aspiration form, the interstitial form comparable to the septicemic variety.
ABSCESS AND GANGRENE OF LUNG.
Abscess and gangrene of the lung are degenerative processes dependent upon embolism, or inspiration of infective matter and it is usually assumed that gangrene succeeds upon abscess when the blood or air supply of a part of the pulmonary tissue has been obstructed mechanically or by inflammation. A review of our material adds little to the etiology or pathogenesis of these two lesions, well recognized as they are by veterinarians. As opposed to human beings, lower animals probably suffer more from them, for an explanation of which one can probably look to the B. necrosis or necrophorus, an organism quite common in feed, and acknowledged to be of great importance as a secondary invader during specific infectious diseases. It has been found in embolic abscesses and in the organs in calf diphtheria and similar other conditions. It has been cultivated here twice, once from a lung abscess, once from Kangaroo disease. It doubtless occurs in human necrotizing processes but is seldom emphasized or even heard about; possibly none is due to it or its congeners.
TABLE 10.
_Table giving Analysis of 20 Mammalian and 3 Avian Cases of Abscess and Gangrene of the Lung_
════════════╤═══════════════╤════════════════╤════════ Animal │ Causative │ Pneumonia, │Abscess │condition upper│septic or other │ or │ respiratory │ │Gangrene │ tract │ │ ────────────┼───────────────┼────────────────┼──────── Sooty │Negative │Catarrhal │Gangrene Mangabey │ │pneumonia │ Cercocebus │ │ │ fuliginosus │ │ │ │ │ │ Rhesus │Negative │Septic from │Abscess Macaque │ │suppurating │ Macacus │ │gland │ rhesus │ │ │ Am. Wild Cat│Aspiration │ │Gangrene Felis ruffus│vomitus from │ │ │violent │ │ │gastroenteritis│ │ │ │ │ │ │ │ │ │ │ Puma Felis │Acute purulent │No │Abscess concolor │nasopharyngitis│ │and │ │ │gangrene │ │ │ │ │ │ Ichneumon │Negative │Sepsis, scalp │Abscess Herpestes │ │wound │ mungo │ │ │ │ │ │ │ │ │ Raccoon │Negative │Pneumonia │Abscess Procyon │ │followed by │ lotor │ │sepsis │ │ │ │ │ │ │ Skunk │Cellulitis face│Sepsis, very │Abscess Mephitis │and neck │mild │ mephitica │ │ │ Puma Felis │Perforating │Secondary │Abscess concolor │abscess around │terminal │ │jaw │pneumonia, │ │ │sepsis │ │ │ │ │ │ │ Porcupine │Negative │Enteritis, no │Abscess Erethizon │ │special sepsis │ dorsatus │ │ │ │ │ │ │ │ │ │ │ │ Kangaroo Rat│Negative │Right sided │Abscess Perodipus │ │bronchopneumonia│ richardsoni │ │ │ │ │ │ Squirrel │Abscess under │No │Abscess Sciurus p. │eye and in │ │ carolinensis│masseter muscle│ │ │ │ │ │ │ │ │ │ │ Mule Deer. │Actinomycosis? │Arthritis. │Abscess Mazama │nasopharynx │Myositis │and hemionus │ │Tenosynovitis │gangrene │ │ │ │ │ │ Axis Deer. │Negative │Negative │Abscess Cervus axis │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ Tapir. │Abscess of │Died from │Abscess Tapirus │parotid │enteritis │ indicus │ │ │ │ │ │ │ │ │ │ │ │ Gazelle. │Negative │Sepsis from │Abscess Gazella │ │infected wound │ isabella │ │ │ │ │ │ │ │ │ Kangaroo. │Negative │Catarrhal │Abscess Macropus │ │pneumonia │and rufus │ │ │gangrene │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ Kangaroo. │Kangaroo │Sepsis │Abscess Macropus │mycosis of jaw │ │ rufus │ │ │ │ │ │ Kangaroo. │Kangaroo │ │Abscess Macropus │mycosis of jaw │ │ giganteus │ │ │ │ │ │ Kangaroo. │Negative │Sepsis from │Abscess Macropus │ │infected wound │ robustus │ │ │ Devil. │Negative │Negative sepsis │Abscess Sarcophilus │ │ │ ursinus │ │ │ │ │ │ │ │ │ Crow. │Negative │Filaria in │Abscess Gymnorhina │ │blood? │ leuconota │ │ │ Heron. Ardea│Negative │Negative │Abscess tricolor │ │ │ ruficollis │ │ │ │ │ │ │ │ │ Goose. Anser│Syngamus in │Negative │Abscess fabalis │trachea │ │ │ │ │ │ │ │ │ │ │ │ │ │ ────────────┴───────────────┴────────────────┴────────
════════════╤═════════╤══════════════╤══════════════ Animal │Single or│ Position │ Bacteria │Multiple │ │ │ │ │ │ │ │ ────────────┼─────────┼──────────────┼────────────── Sooty │Massive │Upper part │Streptothrix, Mangabey │single │lower lobe and│necrosis Cercocebus │ │adherent part │bacillus. fuliginosus │ │upper lobes │ │ │left side │ Rhesus │Single │Occupied │ Macaque │ │nearly all │ Macacus │ │right middle │ rhesus │ │lobe │ Am. Wild Cat│Bilateral│Right middle │ Felis ruffus│ │lobe, left │ │ │lower lobe, │ │ │left bronchus │ │ │ruptured, │ │ │right middle │ │ │lobe ruptured │ Puma Felis │Bilateral│Right upper │Streptococcus concolor │ │and left lower│pyogenes. │ │lobe abscesses│ │ │biggest, right│ │ │middle also │ Ichneumon │Bilateral│Scattered │ Herpestes │ │small │ mungo │ │abscesses, │ │ │under pleura │ │ │especially │ Raccoon │Bilateral│Probably all │ Procyon │ │lobes, right │ lotor │ │middle │ │ │contains │ │ │largest │ Skunk │Single │Left lower │ Mephitis │ │lobe, single │ mephitica │ │small │ Puma Felis │Bilateral│Numerous small│ concolor │ │abscesses, │ │ │irregularly │ │ │scattered │ │ │through both │ │ │lungs │ Porcupine │Bilateral│Multiple small│ Erethizon │ │scattered. │ dorsatus │ │Parasitic? No │ │ │notes │ │ │parasites or │ │ │bacteria │ Kangaroo Rat│Single │Left lower │ Perodipus │ │lobe, small │ richardsoni │ │abscess, │ │ │record scanty │ Squirrel │Multiple │Left lung │ Sciurus p. │ │scattered, │ carolinensis│ │small │ │ │abscesses, │ │ │parasites not │ │ │seen │ Mule Deer. │Bilateral│Scattered both│ Mazama │ │lobes under │ hemionus │ │pleura, upper │ │ │right inferior│ │ │tip gangrenous│ Axis Deer. │Single │Apparently │Streptothrix. Cervus axis │ │primary │ │ │streptothrix, │ │ │abscess in │ │ │cardiac tip of│ │ │upper lobe │ │ │with extension│ │ │toward hilum │ Tapir. │Bilateral│Multiple │Staphylococci. Tapirus │ │subpleural pus│ indicus │ │pockets, │ │ │surrounded by │ │ │catarrhal │ │ │pneumonia │ Gazelle. │Bilateral│Multiple │ Gazella │ │subpleural and│ isabella │ │internal, both│ │ │lungs about │ │ │the same │ Kangaroo. │Double │Lower middle │Pneumococci Macropus │left │left lobes, │streptothrix. rufus │ │seat of a │ │ │ruptured │ │ │gangrene │ │ │surrounded by │ │ │pneumonia, │ │ │right lung │ │ │pneumonic │ Kangaroo. │Bilateral│More on right │Streptothrix, Macropus │ │side, sharply │cocci. rufus │ │outlined │ │ │abscesses │ Kangaroo. │Single │Abscess and │Streptothrix Macropus │ │atelectasis, │ giganteus │ │right middle │ │ │lobe │ Kangaroo. │Single │Lower right │ Macropus │ │lobe │ robustus │ │ │ Devil. │Multiple │Largest middle│Probably Sarcophilus │ │of right lung,│streptothrix. ursinus │ │many small │ │ │scattered │ │ │abscesses. │ Crow. │Multiple │Scattered tiny│ Gymnorhina │ │abscesses, no │ leuconota │ │worms seen │ Heron. Ardea│Single │Upper pole, │ tricolor │ │right lung, no│ ruficollis │ │apparent │ │ │antecedent │ │ │cause │ Goose. Anser│Single │Lower half │ fabalis │ │right lung │ │ │occupied by │ │ │abscess, which│ │ │has penetrated│ │ │air sac │ ────────────┴─────────┴──────────────┴──────────────
The distribution of abscess and gangrene in the lungs in terms of the antecedent disease, therefore its causation, may however be of interest. The lower animals move more in the horizontal position, they seldom cough, they are subject to several different diseases with principal lesions in the anterior head (diphtheria, actinomycosis, etc.) but not to chronic lymphatic infection, they push their snouts into all kinds of filth thereby probably taking into the nose and throat many objects which can find their way to the bronchi, and finally they are not subjected to various instrumental operative procedures when they chance to have a focus of pathology in the nasopharynx. For these reasons the position of abscess and its sequels may be instructive. It has recently been stated that abscesses of the lung in human beings following anesthesia for infections of the upper respiratory tract, occur most often in the upper parts of the lung whereas those following pneumonia develop more in the lower lobes. For the animals of this series, these facts are not borne out. In the accompanying list will be found our acceptable cases of abscess and gangrene. Little can be said about incidence save the fact that the highest percentage and number occur in the Carnivora. It will be found that the right lung is affected nine times predominatingly while the left lung is affected seven times. The lobe most often singled out for an isolated lesion is the lower left, the right middle being the next most often affected. These figures concern the mammals alone, the three birds being considered too few to discuss. It cannot be said from these figures that there is in animals any definite distribution of pulmonary abscess and gangrene.
Nor do these figures correspond to those appearing in literature of human pathology. In man inspiration of foreign bodies, including bacteria-laden mucus, usually carries them into the right lung because of the larger and more directly vertical bronchus to that side. Emboli go as a rule also to the right lung more than to the left because of the greater size of the pulmonary artery and more direct blood current to that side. In these animals right side lesions are more numerous but the left lower lobe is the principal segment of the lung to be affected. The cases are too few and the anatomy too variable to permit any deductions. There is in the affected animals no uniform anatomical peculiarity which would explain the predominance of the right lung as a whole or the left lower lobe as a unit.
PNEUMONOKONIOSIS.
Pneumonokoniosis, because of its importance in industrial diseases, has been subjected during recent years to considerable intensive study in human medicine, from which activity some interesting and useful information has been obtained as to its genesis and effect upon the function of the lung. This condition is of course a purely environmental one, the degree and particular kind of “dusting” being dependent upon the duration and nature of exposure of the particular individual. This Garden is situated beside an active railroad trunk line so that the opportunity for coal dust inhalation is continuous. The degree of anthracotic pigmentation of the lungs and related serous membranes is really negligible and with one questionable exception, we have not seen fibrosis due to this cause in any animal. The one exception, an amazon presented and living in the Garden but three months, at necropsy showed an interstitial chronic bronchitis and pneumonitis stretching out from the hilum, all of the affected area being deeply pigmented. The picture was comparable to what might be expected from a second degree anthracotic fibrosis of Landis and Pancoast. Many specimens come to autopsy with some grade of pigmentation, but none, except the one above, with resultant fibrosis. The degree of anthracosis is usually so slight that it has been considered important enough to include in the diagnosis but eighteen times and curiously enough seventeen of these were observed in birds. Were there more cases it might be profitable to plot their exhibition period but the use of this small number might lead to error; the average length of exhibition of the birds was about a year. It is common to observe some black specklings of the air sacs, as if pepper were dusted on them as has been said before, but even this is rarely marked. It is most often seen in the Anseres, Psittaci and Struthiones but a goodly number of cases occur in the long-lived Passeres.
The distribution of the pigment is essentially the same throughout Mammalia—peribronchial, submucous and in the lymph nodes at the root of the lung. In the birds it is first seen in the subepithelial spaces of the septa of the small alveoli where they project into the secondaries, later accumulating in the connective tissue of the main septa. Collections under the pleura and at the root of the lung are rare, the dust usually spreading out along the air passages into the air sacs.
Other forms of pneumonokoniosis are unknown. Although animals must inspire much dust from dry feed and from floors it must be caught early and removed by snorting or by the lymphatic drainage. It seems fairly well accepted that dusts are dangerous to the degree that they contain inorganic substance and as these animals are not exposed to concentrated mineral or metallic dusts, no effects are seen.
INFARCTION OF LUNG.
Infarctions of the lung, while not at all common, are interesting because of their incidence in the Carnivora and in the distribution. The figures concern the mammals only since the decision for or against infarct in the birds is very difficult because of the frequency in this class of hemorrhage with pulmonary congestion. There were eleven single or double non-septic infarcts, of which seven occurred in Carnivora, one in an ungulate, two in Primates and one in a rodent. The existence of parasites was excluded in most of the cases but could not be entirely in all. Eight of these infarcts were on the left side, five of these being in the lower lobe.
EMPHYSEMA.
Emphysema of the atrophic and chronic vesicular types with the soft, fluffy, pigmented or pale pink organ has not occurred in the animals under observation. Acute vesicular emphysema, such as is seen in chronic bronchial and cardiac diseases, has been encountered several times. Cardiac lesions were found four times, nephritis eleven times, acute enteric conditions seven times, hepatic diseases seven times. Two cases of wide spread amyloid disease showed a deposit of this substance in the alveolar walls. It is quite common to find some grade of emphysema in monkeys dying from osteomalacia and rickets. The process is then most prominent in the upper lobes and along the free anterior margins. The incidence in the orders is Primates 5, Lemures 2, Carnivora 2, Pinnipedia (drowning) 1, Rodentia 1, Ungulata 4, Marsupialia 4. The best example was found in a Skunk (_Mephitis mesomelas_) having a general infection, emanating from the cranial sinuses, and cardiac dilatation. Emphysema does not seem to occur in birds for only one was seen which seemed to present this condition. This was a Bald Eagle (_Haliæetus leucocephalus_) with chronic renal and enteric disease and cardiac hypertrophy. The lungs were tensely distended under their serous covering and showed a few small bullæ anteriorly. Unfortunately a histological preparation is not at hand.
TUMORS.
Tumors of the lung are moderately common, both of primary and secondary origin. Thus we have seen three primary and six metastatic growths in mammals and one of each kind in birds. The primaries were: carcinomata in a civet (_Viverra tangalunga_), a bandicoot (_Thylacomys lagotis_), a kangaroo (_Macropus rufus_), and a lorikeet (_Glossopsittacus concinnus_). The secondaries were: carcinomata in a black bear (_Ursus americanus_), a polar bear (_Ursus maritimus_), a lion (_Felis leo_), and a dasyure (_Dasyurus maculatus_); sarcomata in a prairie wolf (_Canis latrans_), and a raccoon-like dog (_Canis procyonoides_); adenocarcinoma in a chestnut-eared finch (_Amadina castanotis_).
The histological character of the primary cancers would place them in group of the nodular and infiltrative types of Kauffman. They all seem to have taken their origin from the smaller bronchi, the usual starting point. The growths were small in the civet and bandicoot and strongly suggest that the tumors arose in bronchi occupied by parasites; such bodies could not be demonstrated. It is the usual thing to find in cases of parasitism of the bronchi that if there be no ulcerative destruction of tissue the epithelium undergoes some form of hyperplasia, and even structural metaplasia in the air tubes supplied with cuboidal or cylindrical cells. Epithelia many layers deep have been encountered, usually arranged in orderly fashion but frequently “papillomatoid,” suggesting the epidermal layers yet not so far as to show protoplasmic bridges. Distention of various degrees, affected by the contents of the tube and the surrounding inflammation, are common. Such a picture naturally resembles epithelioma and indeed growths of this nature are reported as due to verminous pneumonitis.
There are, especially in cats and dogs, small scattered adenomatoid growths[21] under the pleura and in the pulmonary substance, thought to originate in the alveolar epithelium and occasionally growing to large size; the case in the kangaroo may have had this origin. _It was the only primary tumor to give metastasis_ (to the spleen and gastric wall), the secondaries being decidedly adenomatous in character.
Metastatic growths come from the following originals: two from the thyroid, well known to give pulmonary embolism in dogs; one each from the breast, uterus, adrenal, intestine and kidney. The form assumed is a gray and red mass lying under the pleura or an isolated nodule in the substance. Sarcomatosis, the form apparently spreading out from the hilum and growing in isolated grayish tubercular masses, has not been seen.
THE PLEURA.
The pleura is a tissue apparently quite susceptible to infection in mammals and so closely associated with the air sacs in birds as to be a part of the same membrane, therefore the two being affected together. Throughout the higher class all orders give copious examples of the involvement of the pleura, principally of course as an accompaniment or a sequel to pneumonitic or bronchitic processes but also as a part of acute infectious diseases, such as hemorrhagic septicemia, pleuropneumonia and the like. However two orders present such a number of instances of pleuritis that they deserve notice. The seals, Pinnipedia, of which we have twenty autopsy records, showed inflammation of this membrane four times, three of which were dependent upon pulmonary infection and one apparently due to general septicemia with trifling damage to the lung proper. One of the first cases had gone on to empyema of the classical type, a shrivelled dry almost carnified lung with a thick fibrinopurulent covering. The lung of the seal is well divided into lobules, the external surface being generously supplied with lymphatic channels under the pleura, an arrangement which should carry away infection one would think. Perhaps this high percentage of pleurisy in our Pinnipedia is but accidental. The marsupials, while having a notable percentage of pleurisy both among all the cases and in relation to the number of postmortems, are not so striking from the etiological standpoint since practically all of these have suffered with Kangaroo mycosis or pneumonia. In over half the cases of this infectious disease some grade of pleuritic exudate has been observed, only one, however, going to the stage of empyema.
One cannot speak so definitely of pleuritis in birds since this tissue merely represents in them the covering of the lung and is firmly attached posteriorly to the ribs and anteriorly to the air sacs. Exudates show as collections upon the air sac side of the combined membrane, pleuritis proper in birds being an infiltrative affair coming through the pulmonary tissue and therefore being a part of pneumonitis. I notice a tendency in a few articles to write of pleuritis when the process is confined to the thorax but this gives the impression that the disease is peculiar. There seems no difference in the gross and minute appearance between thoracic serositis and panserositis. The course of procedure seems to be from the anterior or mesial pulmonary ostia into respectively the cervical and thoracic air sacs and this seems to hold good whether the infection be mycosis or fowl cholera or fowl pest. There are records of 104 cases of serositis in birds of which 45 were among parrots, the remainder being well distributed among the various orders; only two each occurred in Galli and Anseres, orders prominently affected under domestication. This high percentage of pleuroperitonitis among parrots and their congeners can only be explained upon the ground of a continued infection of our stock by the virus of fowl cholera and by mould. One case of undoubted fowl cholera occurred recently and as the records are reviewed a few are discovered where the organism was found. The virus must be of low grade for we have had no severe and devasting epizoötic. Mycosis is constantly with us no matter what we do in hygienic measures. There was a small group of cases of pulmonary and serous membrane mycosis combined with staphylococcus infection which carried off six birds. The pathology of this group was interesting because one could follow the infection of the bacterium. The anterior pulmonary ostium was surrounded or covered by a mycotic mass and spreading downward from this was a grayish yellow turbidity of the air sac walls with a delicate sticky or almost mucilaginous exudate extending into the lateral abdominal and posterior sacs.
[Illustration:
FIG. 12.—ENDOTHELIOMA OF PLEURA. LEOPARD (FELIS NEBULOSA). ]
[Illustration:
FIG. 13.—ENDOTHELIOMA OF PLEURA IN FIG. 12. DETAIL OF ONE OF THE WARTY EXCRESCENCES. ]
There is on record one tumor of the pleura, an endothelioma, in a Clouded Leopard (_Felis nebulosa_). It was the usual plate-like thickening with warty excrescences. No metastases occurred. (Figs. 12 and 13).
SECTION VII THE ALIMENTARY TRACT.