PART I

TUBERCULOSIS.

Nearly all infectious diseases have either a limited natural zoological distribution or are encountered chiefly in one order or division. Thus typhoid fever is peculiar to man, hog cholera to swine, foot-and-mouth disease to cows. A second group, including for example anthrax, variola, hemorrhagic septicemia and malignant edema, is somewhat less specific, and may occur in several varieties. There is no more widespread, important infection, zoologically, economically and hygienically, than tuberculosis, and it would seem that all kinds of vertebrates are subject to it. Its manifestations too, are sufficiently similar to support the idea that there must have been originally a common ancestor of the viruses which we now designate separately by a term to indicate their immediate source (human, avian, etc.), and moreover it has been shown that any of the artificially separated varieties or subspecies may under certain circumstances infect all zoological families.

There is, however, a varying resistance to the tubercle bacillus, certain zoological groups standing out preëminently as more or less susceptible to it. There is also a tendency for each animal group to present features more or less peculiar to itself, but nevertheless the characteristics, both gross and minute, of the disease caused by the _Bacillus tuberculosis_ are sufficiently similar to permit close analogy and to establish a diagnosis when the bacteria are found.

The data collected at this Garden are well suited to elucidate the susceptibility of wild animals under captive conditions and to illustrate the nature of lesions in them. Perhaps they do not offer a perfect cross section of zoological distribution of tuberculosis because of the predominance in the display of birds, of monkeys and of ungulates, but the figures will be found significant in certain respects. Such records cannot be compared with those obtained for domesticated animals in farms or breeding places, nor can our material be used to show the incidence for individual species, such as cows, dogs and the like, in a manner commonly used in veterinary literature. Those who are interested in this phase of the problem can find in Lubarsch- Ostertag’s _Ergebnisse_, 1917–18, No. 2, a summary by Eber of all recent literature, covering nearly 1,700 references, which really amounts to a review of all modern knowledge of tuberculosis in the lower animals. The article does not, however, attempt to compare or contrast the incidence per order or family in wild varieties since little information is available on these points. There are no reliable data concerning the existence of tuberculosis in the wild. It is noted in the report of the British Tuberculosis Commission that monkeys were received with this disease; Eber mentions that wild swine from a private preserve presented undoubted evidence of tuberculosis and another similar experience with pheasants, but these and other citations can give no proper estimate of exact conditions nor allow a decision that the infection exists at all under natural environment for in all cases the association with human beings or domesticated animals cannot be excluded. Tuberculosis is usually described as a disease of civilization and its incidence surely varies directly with crowding.

THE TABLE.

Description of Table 23. The study of our autopsy records was begun by the preparation of the accompanying table, which is based first upon the zoological classification per order with subdivisions for families where there are sufficient examples within important orders, and second, upon percentage of total cases. For the analysis of the pathological types, headings of probable origin, gross anatomical lesions and visceral distribution were then made. The first vertical column shows the total autopsies per order, and where families are given, for each of them. In three instances Primates, Ungulata and Galli, not all families are represented, so that the total for the order is greater than that for the subdivisions quoted. It is noteworthy that we have had no tuberculosis among nine families of ungulates; this will be discussed later. The second column gives the total cases of tuberculosis for the order and family, respectively, followed by a third line of percentages. For the analysis of the pathology in these animals all the protocols were reviewed. Forty-eight of them being found unsuitable, deductions were made according to the natural group, thereby leaving the number shown in the fifth column for separation according to origin and type. Analyses in the succeeding columns are made upon number of cases and not upon percentages, because of the confusion arising from small decimals. The actual relationships will be pointed out in the notes. Percentage is not so necessary because comparisons and contrasts are usually made with classes or orders where the figures are comparable.

TABLE 23. _Analytical Table Showing Incidence of Tuberculosis per Order and for Some of the Principal Families, to Which are Added Columns Showing Probable Origin of Infection, Pathological Type of the Disease and the Visceral Distribution of the Morbid Process._

════════════════════╤═════════╤════════════╤══════════╤════════════ Order Family │ No. of │ Cases of │Percentage│ Cases not │autopsies│Tuberculosis│ │sufficiently │for order│ │ │ described │or family│ │ │for analysis ────────────────────┼─────────┼────────────┼──────────┼──────────── „ „ │ „ │ „ │ „ │ „ │ │ │ │ │ │ │ │ │ │ │ │ ────────────────────┼─────────┼────────────┼──────────┼──────────── Primates │ 498│ 192│ 38.5│ 8 Simiadæ │ 7│ 3│ 43.│ 0 Cercopithecidæ│ 353│ 171│ 48.4│ 8 Cebidæ │ 106│ 18│ 16.9│ 0 Lemures, Lemuridæ │ 86│ 23│ 26.7│ 3 Carnivora │ 481│ 17│ 3.5│ 4 Rodentia │ 199│ 5│ 2.5│ 0 Ungulata │ 365│ 35│ 9.6│ 2 Equidæ │ 11│ 1│ 9.│ 0 Bovidæ │ 123│ 12│ 9.7│ 1 Cervidæ │ 171│ 19│ 11.1│ 1 Camelidæ │ 25│ 3│ 12.│ 0 Proboscidea │ 3│ 2│ 66.│ 0 ────────────────────┼─────────┼────────────┼──────────┼──────────── Totals for Mammalia │ [97]1860│ [97]274│ [97]14.7│ 17 Passeres │ 1355│ 18│ 1.3│ 6 Picariæ │ 87│ 11│ 13.│ 0 Psittaci │ 698│ 38│ 5.4│ 3 Loriidæ │ 24│ 3│ 12.5│ 0 Cacatuidæ │ 80│ 7│ 8.7│ 1 Psittacidæ │ 585│ 28│ 4.8│ 2 Striges │ 133│ 6│ 4.5│ 3 Accipitres │ 196│ 11│ 5.6│ 1 Columbæ, Columbidæ │ 157│ 50│ 32.│ 5 Galli │ 299│ 42│ 14.│ 5 Phasianidæ │ 252│ 22│ 8.3│ 3 Cracidæ │ 38│ 17│ 44.│ 1 Megapodidæ │ 5│ 3│ 60.│ 1 Fulicariæ │ 35│ 9│ _27._│ 0 Hemipodii │ 2│ 1│ _50._│ 0 Alectorides │ 37│ 10│ _27._│ 2 Odontoglossæ │ 6│ 2│ _33._│ 1 Anseres │ 317│ 16│ 5.│ 5 Struthiones │ 32│ 3│ _9.4_│ 0 Crypturi │ 5│ 2│ _40._│ 0 ────────────────────┼─────────┼────────────┼──────────┼──────────── Totals for Aves │ [97]3505│ [97]219│ [97]6.2│ 31 ────────────────────┼─────────┼────────────┼──────────┼──────────── Grand Totals │ [98]5365│ [98]493│ [98]9.1│ 48 ────────────────────┴─────────┴────────────┴──────────┴────────────

════════════════════╤════════╤══════════════════════╤═══════════════ Order Family │Net no. │ Probable origin │Pathological Type │of cases│ │ │ in │ │ │analysis│ │ ────────────────────┼────────┼──────────┬───────────┼───────┬─────── „ „ │ „ │Pulmonary-│Intestinal-│ Acute │Massive │ │aerogenic │ lymphatic │Miliary│caseous │ │ │ │ │ │ │ │ │ │ ────────────────────┼────────┼──────────┼───────────┼───────┼─────── Primates │ 184│ 86│ 98│ 3│ 52 Simiadæ │ 3│ 3│ │ │ 2 Cercopithecidæ│ 163│ 76│ 87│ 2│ 46 Cebidæ │ 18│ 7│ 11│ 1│ 3 Lemures, Lemuridæ │ 20│ 6│ 14│ │ 5 Carnivora │ 13│ 6│ 7│ │ 1 Rodentia │ 5│ 3│ 2│ │ 3 Ungulata │ 33│ 27│ 6│ │ 6 Equidæ │ 1│ │ 1│ │ 1 Bovidæ │ 11│ 10│ 1│ │ 1 Cervidæ │ 18│ 14│ 4│ │ 4 Camelidæ │ 3│ 3│ │ │ Proboscidea │ 2│ 2│ │ │ ────────────────────┼────────┼──────────┼───────────┼───────┼─────── Totals for Mammalia │ 257│ 130│ 127│ 3│ 67 Passeres │ 12│ 9│ 3│ │ 5 Picariæ │ 11│ 1│ 10│ │ 2 Psittaci │ 35│ 13│ 22│ 1│ 9 Loriidæ │ 3│ 1│ 2│ │ 1 Cacatuidæ │ 6│ 4│ 2│ │ 1 Psittacidæ │ 26│ 8│ 18│ 1│ 7 Striges │ 3│ 3│ │ │ 1 Accipitres │ 10│ 5│ 5│ │ 2 Columbæ, Columbidæ │ 45│ 10│ 35│ │ 12 Galli │ 37│ 10│ 27│ │ 12 Phasianidæ │ 19│ 2│ 17│ │ 4 Cracidæ │ 16│ 7│ 9│ │ 7 Megapodidæ │ 2│ 1│ 1│ │ 1 Fulicariæ │ 9│ 1│ 8│ │ 1 Hemipodii │ 1│ 1│ │ │ 1 Alectorides │ 8│ │ 8│ │ 2 Odontoglossæ │ 1│ │ 1│ │ Anseres │ 11│ 2│ 9│ │ 4 Struthiones │ 3│ 3│ │ │ Crypturi │ 2│ │ 2│ │ ────────────────────┼────────┼──────────┼───────────┼───────┼─────── Totals for Aves │ [99]188│ 58│ 130│ 1│ 51 ────────────────────┼────────┼──────────┼───────────┼───────┼─────── Grand Totals │ [99]445│ 188│ 257│ 4│ 118 ────────────────────┴────────┴──────────┴───────────┴───────┴───────

════════════════════╤════════════════════════╤════════════════════════ Order Family │ Pathological Type │ Visceral Distribution │ │ │ │ │ │ ────────────────────┼───────┬──────────┬─────┼─────┬─────┬──────┬───── „ „ │Nodular│ Chronic │Pearl│Lungs│Liver│Spleen│Lymph │caseous│ fibrous │type │ │ │ │nodes │ │ and │ │ │ │ │ │ │ulcerative│ │ │ │ │ ────────────────────┼───────┼──────────┼─────┼─────┼─────┼──────┼───── Primates │ 108│ 16│ 5│ 173│ 122│ 149│ 145 Simiadæ │ │ │ │ 3│ 2│ 3│ 3 Cercopithecidæ│ 96│ 16│ 3│ 156│ 111│ 136│ 128 Cebidæ │ 12│ │ 2│ 14│ 9│ 10│ 14 Lemures, Lemuridæ │ 15│ │ │ 17│ 14│ 17│ 12 Carnivora │ 8│ 4│ │ 11│ 4│ 2│ 6 Rodentia │ 2│ │ │ 4│ 2│ 2│ 4 Ungulata │ 1│ 24│ 2│ 28│ 7│ 3│ 25 Equidæ │ │ │ │ │ │ │ 1 Bovidæ │ 1│ 9│ │ 9│ 4│ 2│ 7 Cervidæ │ │ 13│ 1│ 17│ 2│ │ 14 Camelidæ │ │ 2│ 1│ 2│ 1│ 1│ 3 Proboscidea │ │ 2│ │ 2│ │ │ ────────────────────┼───────┼──────────┼─────┼─────┼─────┼──────┼───── Totals for Mammalia │ 134│ 46│ 7│ 235│ 149│ 173│ 192 Passeres │ 7│ │ │ 9│ 5│ 5│ Picariæ │ 8│ │ 1│ 2│ 9│ 6│ 1 Psittaci │ 25│ │ │ 18│ 24│ 14│ 2 Loriidæ │ 2│ │ │ 3│ 3│ 1│ Cacatuidæ │ 5│ │ │ 5│ 5│ 2│ Psittacidæ │ 18│ │ │ 10│ 16│ 11│ 2 Striges │ 2│ │ │ 3│ 3│ 2│ Accipitres │ 7│ 1│ │ 8│ 6│ 8│ 1 Columbæ, Columbidæ │ 33│ │ │ 24│ 40│ 34│ 1 Galli │ 24│ 1│ │ 20│ 34│ 29│ 2 Phasianidæ │ 15│ │ │ 7│ 18│ 15│ 1 Cracidæ │ 8│ 1│ │ 12│ 15│ 13│ Megapodidæ │ 1│ │ │ 1│ 1│ 1│ 1 Fulicariæ │ 8│ │ │ 4│ 8│ 8│ 1 Hemipodii │ │ │ │ 1│ 1│ 1│ Alectorides │ 6│ │ │ 4│ 8│ 7│ 2 Odontoglossæ │ 1│ │ │ │ 1│ 1│ Anseres │ 5│ 2│ │ 4│ 7│ 8│ 1 Struthiones │ │ 3│ │ 3│ 2│ 3│ 2 Crypturi │ 2│ │ │ 1│ 2│ 2│ ────────────────────┼───────┼──────────┼─────┼─────┼─────┼──────┼───── Totals for Aves │ 128│ 7│ 1│ 101│ 151│ 128│ 13 ────────────────────┼───────┼──────────┼─────┼─────┼─────┼──────┼───── Grand Totals │ 262│ 53│ 8│ 336│ 300│ 301│ 205 ────────────────────┴───────┴──────────┴─────┴─────┴─────┴──────┴─────

════════════════════╤══════════════════════════════════════════════════════ Order Family │ Visceral Distribution │ │ │ ────────────────────┼─────────┬──────┬─────────┬──────┬─────┬─────┬──────── „ „ │Intestine│Kidney│ Serous │Bones │Brain│Heart│Pancreas │ │ │membranes│ and │ │ │ │ │ │ │joints│ │ │ │ │ │ │ │ │ │ ────────────────────┼─────────┼──────┼─────────┼──────┼─────┼─────┼──────── Primates │ 30│ 84│ 70│ 2│ 2│ 7│ 3 Simiadæ │ 2│ 1│ 1│ │ │ │ Cercopithecidæ│ 24│ 76│ 63│ 2│ 2│ 7│ 2 Cebidæ │ 4│ 7│ 6│ │ │ │ 1 Lemures, Lemuridæ │ 2│ 7│ 1│ │ │ │ 1 Carnivora │ 1│ 4│ 3│ 1│ │ │ Rodentia │ 1│ 2│ 2│ 1│ │ │ Ungulata │ 1│ 2│ 7│ │ │ │ Equidæ │ │ │ │ │ │ │ Bovidæ │ 1│ 1│ 1│ │ │ │ Cervidæ │ │ │ 5│ │ │ │ Camelidæ │ │ 1│ 1│ │ │ │ Proboscidea │ │ │ │ │ │ │ ────────────────────┼─────────┼──────┼─────────┼──────┼─────┼─────┼──────── Totals for Mammalia │ 35│ 99│ 83│ 4│ 2│ 7│ 4 Passeres │ 4│ │ 4│ │ │ │ Picariæ │ 4│ 1│ 3│ 1│ │ │ Psittaci │ 12│ 6│ 6│ │ │ 1│ Loriidæ │ 1│ 1│ 1│ │ │ │ Cacatuidæ │ │ 1│ 1│ │ │ 1│ Psittacidæ │ 11│ 4│ 4│ │ │ │ Striges │ │ │ 3│ │ │ │ Accipitres │ 4│ 3│ 6│ │ │ 2│ Columbæ, Columbidæ │ 16│ 13│ 20│ │ │ 1│ Galli │ 20│ 7│ 15│ │ │ │ 1 Phasianidæ │ 10│ 2│ 6│ │ │ │ 1 Cracidæ │ 10│ 5│ 7│ │ │ │ Megapodidæ │ │ │ 2│ │ │ │ Fulicariæ │ 3│ 3│ 4│ │ │ │ Hemipodii │ 1│ 1│ 1│ │ │ │ Alectorides │ 3│ 3│ 7│ │ │ │ Odontoglossæ │ 1│ │ │ │ │ │ Anseres │ 3│ 4│ 4│ │ │ │ Struthiones │ │ 1│ 1│ │ │ │ Crypturi │ 2│ 1│ │ │ │ │ ────────────────────┼─────────┼──────┼─────────┼──────┼─────┼─────┼──────── Totals for Aves │ 73│ 43│ 74│ 1│ 0│ 4│ 1 ────────────────────┼─────────┼──────┼─────────┼──────┼─────┼─────┼──────── Grand Totals │ 108│ 142│ 157│ 5│ 2│ 11│ 4 ────────────────────┴─────────┴──────┴─────────┴──────┴─────┴─────┴──────── See page 484, for description of tabulation. For meaning of italics see foot note Table 1. These and figures set opposite them are cases not percentages.

It is generally conceded that the principal and only significant routes of origin for tuberculosis are via the respiratory and alimentary tracts. The criteria upon which to decide the route that has been followed are by no means definite and may not be for any given case unexceptionable. In birds the alimentary tract is conceded to be the important one, while in mammals an aerogenic route is believed to be the rule. However, since feeding experiments have shown that tubercle bacilli can gain the lungs by passing through the intestinal wall and abdominal lymphatics without leaving gross traces, the decision that one or the other route has been taken may be erroneous, and statistics therefore can often be fallacious. It is usually the rule to assume that the oldest or best developed lesions occur where the originally settled organisms exerted their maximum effect. The questions of infection-path and of original lesion not having been settled it is obvious that decision as to the route must be in the nature of an estimate. With these limitations in mind I have divided the cases into probable respiratory and alimentary origins according to the following criteria. Where the lesions were wholly respiratory or within the lymph glands of the trachea and bronchi the decision was not so difficult. Predominance of the pulmonary disease with recent lesions in other organs was taken to indicate an aerogenic origin. The chronic ulcerative or fibrous pulmonary lesions were also ascribed to those beginning in the lungs. The alimentary tract was considered for this purpose as beginning in the tonsillar area and ending at the anus. This is as I understand the customary teaching. When the lymph nodes of the alimentary area were advanced in the process, the intestinal method was held responsible. It is of course not to be forgotten that organisms coughed up from the lungs and swallowed may be responsible for lesions within the alimentary system. However, a predominance of intestinal, splenic, hepatic and lymphatic lesions caused me to place the case with those originating from the alimentary tract. Granting the limitations of our knowledge, of the criteria and of my own judgment, it is noteworthy that the results of this division of the table are not contradictory to the usual teaching, the most conspicuous being the predominance of the alimentary infection of Aves and in the order Primates, whereas the pulmonary route has the highest figures for the Ungulata.

The next subdivision of the table concerns the gross pathological type. Beginning with the most acute form, the acute miliary, progression is made in terms of chronicity—then following in order the massive caseous form including caseous pneumonia, the caseous miliary or nodular form so well represented by the monkey, then the fibroulcerative type such as one encounters in human consumption, including also forms in which fibrosis predominates, and lastly the rather uncommon pearl disease. This classification has been relatively easy to follow and can be readily imagined by the reader. There are of course intermediate cases or transition forms and there have been instances partaking of more than one character. The groupings present only gross appearances and, with few exceptions, are not to be taken as direct indications of type incidence in special groups.

Visceral distribution is shown in the last gross section of the table; single cases or unusual locations are not tabulated but will be separately discussed. The visceral distribution is made upon evident gross lesions or their discovery in organs whose condition suggested the need of microscopic study for confirmation. The figures in the table will be reviewed first upon the incidence as a whole and then between classes and orders. This will be succeeded by an analysis of the particulars for each order and then for each of the pathological headings.

TOTAL AND CLASS INCIDENCE.

The autopsies upon 5,365 animals have revealed the existence of tuberculosis in 492, a percentage of 9.1. This means that lesions due to the _Bacillus tuberculosis_ were present, but they were not always the cause of death, since many specimens have been executed and others have had sufficient pathology to kill, aside from the tuberculous changes. Deaths due to the disease alone are difficult to estimate, but seem to be about 325 or 6 per cent. These figures, while they represent the total incidence, lose considerably in significance when the factors are analyzed. Mammalian incidence is 14.7 per cent., Avian 6.2 per cent., but the former is based upon figures obtained from six of twelve orders numbering 1,860 animals, whereas the latter represent the cases in fourteen of twenty orders numbering 3,505 birds. The percentages are considerably increased by high figures for a few orders, Primates, Lemures, Columbæ for examples. There are missing from the list very few orders of which we have any notable number of autopsies, Marsupialia and Herodiones being the only important ones; it would seem that these orders have a high resistance to the disease.

Investigation into the origin of the disease in mammals and birds shows with definiteness the preponderance of the alimentary route influence in the latter, but for the former the figures cannot be said to be conclusive. The bird excretes large numbers of bacilli with the feces thereby soiling the feed and the ground. This is due to the frequency of intestinal open lesions and to the really enormous numbers of bacilli which are in the morbid tissue. I think it can be said with safety that, other things being equal, the bird excretes bacilli constantly and in greater numbers than does the mammal, and that in physically comparable lesions there are more bacilli in the avian than in the mammalian.

The inconclusive figures for the origin of the disease in the mammal can be clarified very little by the subtraction from the tables of the figures for the very susceptible Primates. By doing this it would seem that the respiratory route dominates as 43 to 29, whereas if the reasonably susceptible Lemures be also deducted the ratio becomes as 38 to 15. It would seem that the evidence favors the aerogenic route in the mammal.

PATHOLOGICAL TYPES.

An inquiry into the gross pathological types reveals at once the frequency with which the nodular and massive caseous forms appear. If the number of cases be reduced to percentage it will be found that 59 per cent. of all specimens presented the nodular variety and 26.6 per cent. the massive caseous form. These large figures (equaling when combined 85 per cent.) coupled with the fact that only 12 per cent. of the total were fibroulcerative and 1.8 per cent. of the pearl type, would seem to indicate that the nodular and massive caseous processes are the lesions to be expected in wild animals. Furthermore, if these nodular and caseous forms speak for recent infection or acuteness of the morbid process, it would seem that wild animals have a low tissue resistance to tuberculosis. It is a widespread belief, in some degree well supported, that a disease new to an animal species is highly fatal and that the survival of the race depends upon an active self- immunization or the survival of the pathologically least susceptible. If tuberculosis be a disease of civilization, these figures would suggest that it is absent in nature. As a further support of this idea it can be said that with the exception of two cases in ungulates, no fibroid tuberculosis, approaching the quiescent type as seen in man and rarely in domestic animals, was encountered. Very rarely calcareous deposits will be found in both simian and ungulate lesions but these need not indicate a tendency to general healing although at that place the process may be inactive. The bird uses considerable fibrous tissue in the construction of its tuberculous mass but fibrosis never masters the situation with the formation of scar tissue sufficient to wall off the process. Pearl disease, a fibrocaseous condition, is not a healing fibroid procedure and is, in our material, of no numerical significance.

VISCERAL DISTRIBUTION.

The distribution of the morbid lesions in the viscera presents some interesting features. In the first place the data leave no doubt that the most susceptible tissue in the wild animal body is, as in the case of human and domestic animals, the lung. The susceptibility of this organ in the two classes is however a different matter since in the mammal 91.4 per cent. show pulmonary lesions while only 53.7 per cent. of birds are so affected. Part of the reason for this appears in the figures for the principal abdominal organs, of which the liver and spleen occupy the prominent places. The mammalian livers show 58.2 per cent., the avian 80.3 per cent.; 67.5 per cent. of mammalian spleens, 68.0 per cent. of avian spleens have tuberculous lesions. The figure for the mammalian spleen is distorted because of the peculiar susceptibility of this organ in the monkey, it being conspicuously free of lesions in most mammalian orders. The intestines presented discernible lesions in practically 40 per cent. of birds but only in 13.5 per cent. of mammals. Renal involvement was found in 38.4 per cent. of mammals and 22.9 per cent. of birds.

A study of the changes in the serous surfaces is complicated by the difference of anatomy in the two classes. The mammal has separate closed serous sacs well guarded against invasion from mucous surfaces whereas in the bird the air sacs and serous cavities are closely related, the latter being loosely applied to viscera they are intended to cover. Moreover in Aves direct infection of the air sacs seems a definite possibility. Notwithstanding the fact that the bird’s sacs and serous surfaces appear so open to infection there is no great preponderance of lesions within them—Aves 39.3 per cent. Mammalia 32 per cent. The lymph nodes were tabulated as a tissue rather than according to location, the latter method being found profitable for discussion in a few orders only. As might be expected the abundant lymph nodes of the mammal were affected out of all proportion to those in the bird. These matters will be discussed later. The remaining figures on the table have no comparative value.

ORDINATE CHARACTERISTICS.

The Primates as an order have shown low resistance to tuberculosis, a fact well known to general observation. How much this is due to the unsanitary surroundings to which these naturally free active beasts are subjected, in catching, transporting and storing for sale, must at present remain conjectural, but they are probably infected with ease as our experience in this laboratory suggests. Desiring a tuberculous monkey for certain tuberculin tests, I injected one hundredth of a milligram of a human culture, known to produce definite lesions in rabbits; the animal died in three months with advanced general tuberculosis. The unexpected and interesting feature of our figures is the susceptibility of different families within the order. The Old World monkeys, Simiadæ and Cercopithecidæ have a combined incidence two and one-half times as great as the New World Cebidæ, and the marmosets had no tuberculosis at all in the thirty-two specimens. Possibly this is a matter of transportation and handling, which reduces the resistance and offers chance to infect apes and baboons. The New World capucin monkeys have their exposure too since many of them are household pets before the Garden receives them. Their usual life in captivity is however shorter than that of Old World varieties, they therefore being exposed to infection for a shorter time. It would seem however that American Primates are more resistant to the disease than African and Australasian.

The form of tuberculosis to which this order is liable is well described in text-books, it being so characteristic that the term “monkey tuberculosis” is used to distinguish it. The purpose of the term is to compare the lesions with certain cases of generalized tuberculosis in children. It is characterized by a nodular involvement of the liver and of the spleen particularly, sometimes also of the lungs but in fatal cases the last organ is commonly the seat of massive caseation or caseous pneumonia. The prominence of the pulmonary lesions often makes a decision of origin difficult since important changes may be found in the liver and abdominal nodes. Blair at New York, and Rabinowitsch at Berlin are of the impression that many cases of monkey tuberculosis start by pharyngeal and tonsillar infection because they found cervical adenitis so commonly. Our records and specimens would support this idea in only fourteen instances and I am of the impression that the lower intestinal route is more often responsible, even to a higher figure than is recorded in the table. This view is based upon the frequent occurrence of enlarged glands in the mesentery, retroperitoneum and posterior mediastinum, in the latter location being quite as prominent if not more so than in the bronchial and tracheal area. Occasionally deposits of calcareous matter will be found in old caseous glands but in such animals there has always been some other spot of activity of tuberculosis. The frequency with which the liver and spleen are affected gives opportunity for hematogenic spread, a method of no small importance in the opinion of Eber. The chronic ulcerative form is quite well displayed in monkeys, interestingly enough to cite an illustrative case at the end of this division of the discussion. Five cases of distinct chronic cavitation were encountered; several small recent cavities were found in the massive caseous pneumonic cases. The two acute miliary cases and one of the pearl type will be discussed briefly on a later page.

Despite the prominence of the liver, spleen and lymph nodes, the lungs stand ahead of all others by a safe margin of visceral incidence. The spleen stands in the third place in this order and in the next, Lemures, but in no other mammalian group does this organ occupy so prominent a position. The susceptibility of lymphatic tissue in the monkey is further illustrated by the large number of cases showing lesions in lymph nodes. It is rather striking however that our material showed very few active ulcerations in the lymphoid plaques of the intestinal wall nor indeed do the intestines present a large numerical involvement. Serous membrane tuberculosis is chiefly that of the pleura, upon which early precaseous tubercles are frequently found, usually in conjunction with pulmonary disease. Tuberculous peritonitis of the plastic and nodular variety occurred only six times, though light adhesions to nodules in the liver and spleen were quite common. Pericarditis was found five times, in three of which there was myocardial disease; which of the two was primary was not indicated in the notes but from present reading it would seem that the heart muscle was involved first.

The next order, Lemures, has a susceptibility of about half that of the monkeys judging by the percentage incidence. Analytically the members of this group react quite like the preceding order in having the same types of origin, pathology and organic distribution. Since they are so close zoologically, present similar lesions and are tested in the same manner as the monkeys, we group them together and shall proceed to discuss special cases of interest in both orders.

Special Cases in Primates and Lemures. Acute general miliary tuberculosis occurred thrice in Old World and once in New World monkeys. The first case took its origin in a caseous gland in the bronchotracheal area, the lung showing a minor degree of involvement with milia but no older process. The second took its origin in the mesenteric area and the organs of this section of the body were most affected. The only case in the Cebidæ seemed to be of intestinal origin since an acute plastic peritonitis with fluid exudate accompanied the generally miliary disease.

Pearl disease of the bovine type has been encountered on four occasions but it cannot be said to have developed to the state of perfection seen in the cow. There is lacking the masses of nodules growing together in a fungoid character usually seen on the pleura and peritoneum. The monkey form is in isolated nodules of gray-yellow color which may show caseous centres. The visceral lesions are in firm separate areas not tending to soften or coalesce. Two of these monkeys died from recent pulmonary exacerbations. From one of the cases a bovine bacillus, judging from culture and rabbit virulence, was isolated.

As a good example of monkey tuberculosis, illustrating at the same time a chronic ulcerative pneumonitis with cavitation, the following case is cited:

Green Monkey (_Cercopithecus callitrichus_) ♀ . Was coughing and drooping for two days before death. Chronic ulcerative tuberculosis of lungs with cavity formation; early conglomerate tuberculosis of liver; conglomerate caseous tuberculosis of spleen; early conglomerate tuberculosis of ileum (Peyer’s patches); acute catarrhal enteritis; miliary tuberculosis of right kidney. The animal is well preserved, sleek, with a moderate amount of fat. The left pleura is largely obliterated by adhesions in the lower portion. As lung is freed it is torn, showing a cavity measuring 3 × 3 × 4 cm., which is filled with a curdy gray material. Cavity has well defined walls. Rest of lower lobe in which this cavity lies is solidified, red and edematous and contains numerous conglomerate tubercles. Upper lobe practically free of tubercles; shows compensatory emphysema. The right lung closely resembles the left but lacks the cavity. The liver is enlarged, soft and friable, of red color, spotted yellow. Serous and section surfaces show closely packed early conglomerate tubercles. The spleen is of normal size, soft, has red pulp with large conglomerate tubercles which project slightly on the capsule. The kidneys are apparently normal except for the presence of two or three subcapsular large, solitary tubercles in the right organ. The duodenum has thickened walls, mucosa bright, brilliant scarlet hue. In the ileum the walls are thickened, mucosa bright red, agminated follicles hyperplastic elevated and display several (4–12) miliary tubercles. These may be seen shining through on the serous surface but there is no peritoneal tuberculosis. No ulceration of Peyer’s patches. Contents of large intestine is rather dry and here the mucosa shows exaggerated rugæ which cannot be smoothed out. Walls are thickened, and ulceration, while suggested, cannot surely be determined.

An interesting case of primary tuberculosis in the larynx detected at postmortem after a tuberculin injection is as follows:

[Illustration:

FIG. 51.—BOVINE TUBERCULOSIS IN THE MONKEY. THIS SPECIMEN SHOWS THE BOVINE PEARL DISEASE ON THE COSTAL PLEURA, AND SERVES AS WELL TO ILLUSTRATE THE NODULAR TUBERCLES COMMONLY FOUND IN THE SPLEEN OF ALL PRIMATE TUBERCULOSIS. ]

Black and White Lemur (_Lemur varius_) ♂ . Miliary tuberculosis of larynx; perilaryngitis and retropharyngeal lymphadenitis. Killed because of unsatisfactory chart after injection of tuberculin. The only tuberculous lesion to be found in the body, which is in excellent shape, is in and about the larynx. The lesions within are on the epiglottis, false and true vocal cords and the main ventricle. On either side of the root of the epiglottis, there are a few recent tubercles. The lesion in the retropharyngeal lymphatics is recent and diffuse. This is probably primary as it is not known that the retropharyngeal glands drain to or from the larynx. About the lesions on the laryngeal mucosa there is an area of congestion probably due to the tuberculin injection.

Local lymphatic tuberculosis of comparative interest was encountered a few times. Three cases of cervical adenitis, large enough to be visible, were seen, of which one broke down about two weeks before death, and discharged. The others did not ulcerate through the skin but, contrary to the usual rule for the human being, remained as isolated glands only lightly adherent to one another where they lay adjacent. There was also seen an ulcerating tuberculous lymph node in the groin of one monkey, the animal having rather pronounced abdominal and pelvic tuberculosis. Two instances of tonsillar tuberculosis are recorded, in both of which the lesion was of some duration and associated with caseation in the lymph node lying immediately behind and below it. A Guinea Baboon (_Papio sphinx_) had as an unusual part of his general tuberculosis, an active caseopurulent collection in the antrum of Highmore, which attacked the upper maxilla and immediately adjacent muscle; tubercle bacilli could be demonstrated.

One of the cases of nodular or massive peritoneal tuberculosis is quite like the tumor-forming variety of human adolescents; it is as follows:

Reddish Macaque (_Macacus rufescens_). Caseous tuberculosis of mesentery and spleen; miliary tuberculosis of lungs, pleura and liver; chronic myocarditis. The lymphatic glands of the posterior and superior mediastinum and bronchi are slightly enlarged, soft and anthracotic but do not show any tuberculous change. Both lungs are riddled with small, firm, gray miliary tubercles, some surrounded by a clear mantle of connective tissue. The intervening lung is practically normal. Pleura over base of right lung on both surfaces shows small, pale miliary tubercles. The liver contains various sized miliary tubercles. There is a large caseous mass in posterior end of spleen with adhesions to kidney, stomach and colon. Retroperitoneal glands are much enlarged, firm, homogeneous—probably tuberculosis of a different type. Lesser omentum contains one caseous gland. Few caseous glands in great omentum. In the right iliac region there is a large mass involving many coils of intestine. It is found to arise probably from the ileocecal glands and can be traced along the mesentery to the central lymphatic stalk. The mass involved the tissues of the mesentery and surrounds many coils of intestine. Cecum and first part of colon can be traced over its right side. Rectum is free except on right side where it is lightly attached to the mass. Epicardium is gray and irregularly thickened and the muscle just beneath serous membrane is pale and streaked with red lines.

There have been three cases of tuberculosis of the internal male genital area, one of which was suspected of having been the primary seat of the disease; it was described on page 315. The other two could have been secondary since other points of morbid change were as old or older. One of these cases formed a tumor as large as a goose egg at the vesical neck, obstructing the flow of urine and blocking up the seminal vesical, in consequence of which paralytic distention occurred in the bladder while the vesicles were tightly filled with inspissated semen. A case of Fallopian salpingitis has also been cited. Two instances of cerebral tuberculomata have already been described.

Carnivora. This order has the reputation of being quite resistant to the tubercle bacillus, based upon the relative infrequency among cats and dogs in contrast to cows and swine. Some veterinary statistics cite the incidence up to 5 per cent., and occasional references may be found to tuberculosis in circus lions and tigers. Our records would suggest that in gardens the wild varieties of this order have about as much of the infection as the domestic carnivores, 3.5 per cent. The group is made of six Felidæ, one Viverridæ, three Canidæ, six Procyonidæ, and one Ursidæ. The first family includes a lion, tiger, a jaguar and three smaller cats. The Canidæ are all small foxes. The Procyonidæ are all coatis. The features of this order are the occurrence of the fibroulcerative variety with cavitation in the Felidæ and the caseous nodular abdominal and glandular disease in the coatis. All these animals, even those of the last named variety and pathological type, tend to show some tissue resistance to the tuberculous disease. Connective tissue activity is characteristic of the process, considerable distortion being produced by the fibrosis. This feature is borne out where the tissues are studied microscopically. Definite milia are sometimes found, but they consist of epithelioid and round cells with imperfect caseation, giant cells being often missing. About the miliary tubercles a diffuse and not essentially specific tuberculous granulation tissue is found, mixed with which is much connective tissue growth. The fibrotic adhesion-forming serous membrane tuberculosis of carnivores seems worthy of emphasis by the citing of a case in point. White nosed coati (_Nasua narica_), was received in poor condition and died in a few days. Upon dissection a slightly turbid yellowish fluid was found to occupy what remained of the peritoneal cavity which was reduced in size by dense adhesions of the intestines into an inflammatory mass. The omentum was a diffuse thickened apron, also beset with fine tubercles, lying over the mass. Fine young tubercles could also be found upon the intestines and liver while the mesenteric lymph nodes were early in caseation; thoracic organs not infected.

One of the most interesting cases concerned hypertrophic osteitis in a chronically tuberculous lion; the feet are discussed on page 346. This process was described by Marie for human beings many years ago, and was reported in dogs by Cadiot[100] in 1912. This beast was one of five large cats which have died from tuberculosis in its chronic ulcerative form. Three of the cats, one fox and the bear showed definite cavitations of a ragged loculated form. The cavities were usually of the multiple variety and were found in the posterior, that is lower lobe.

Rodentia. The paucity of cases in this order permits little information to be drawn from the form of tuberculosis. The total seems to have been swollen by a group of three beavers, all of which came in one shipment. The remainder were a Capybara and an Agouti. The general type is that of much caseation with little or no surrounding fibrosis. One illustrative case is cited:

American Beaver (_Castor canadensis_). General tuberculosis. The animal presents generalized tuberculosis. The regional lymph nodes show caseous nodules. The right hip joint shows caseous material about the acetabulum with necrosis and pathological fractures in the os innominatum immediately above the acetabulum and including its cavity. Lungs show almost no normal respiratory tissue, the process being a diffuse precaseous, partly gelatinous pneumonic phthisis. The superior and posterior mediastina show caseous glands. There is miliary tuberculosis of the liver. Nodular caseous tuberculosis of the spleen with small tubercles and some cirrhosis of the intervening tissue. There are caseous nodules in all perirenal glands and in the kidney cortices. The psoas muscle glands are densely caseous. The pelvic organs except about the right acetabulum escape involvement. Adrenals not opened but probably not involved.

Ungulata. This order shows the most definite figures among those for the order of mammals. Nearly one-tenth of the whole number of specimens have had some form of tuberculosis and of a very definite character. It is well at first to mention, however, that only four of thirteen families are represented, from which four came 328 of the total 365 autopsies. The remaining thirty-seven were such animals as tapirs, giraffes, swine, and peccaries, in all of which tuberculosis has been reported from elsewhere.

Pulmonary disease with less prominent lesions in other organs, especially the intestines and their related glands, speaks in favor of the aerogenic route being the common one. This of course has been a bone of contention among veterinarians, and I do not presume to settle the matter with these figures.

This order resists tuberculosis to a certain degree as attested by the fibroulcerative character of the majority of the cases. Two instances, one in a buffalo and one in a deer, showed very highly fibrotic pulmonary lesions with a partial attempt to surround and wall off numerous areas of caseation. So too in this order there is a greater tendency to calcification, both in the intra- and extrapulmonary nodes. It is to be emphasized that in our material the thoracic lymph nodes are affected more than the abdominal and regional as 3 to 1. The apparent immunity of the spleen of this order is well illustrated.

The paucity of serous surface involvements in the wild Bovidæ and their prominence in the Cervidæ cannot be ignored in the figures, but it seems misleading since pleural growths and adhesions are quite common in the domestic Bovidæ. The case in the Equidæ was that of a Zebra with a large tuberculous abscess in the retroperitoneal glands forming a tumor in the left renal region. It was quite well surrounded by fibrosis, and the infection had not extended; it seemed quite recent. Analysis of the figures for the remaining three families of ungulates offers little for contrast and much for comparison; it is the usual picture as seen in the domestic cow. Some special cases are worthy of review.

An interesting specimen of softened glands chiefly on one side of the neck was found in a Fallow deer (_Cervus dama_). It resembled the juvenile human cases that require surgical attention. Although palpable lymph nodes can be found in practically all cases of generalized tuberculosis in the Ungulata, this is the only case in our records in which they have presented a large tumefaction and broken down. Pulmonary cavitation is recorded but thrice, one for each of the last three families. Fibrocaseous tuberculosis of the testes was discovered in a Nylghaie (_Boselaphus tragocamelus_), but there is no knowledge of mating or offspring. An ischiorectal abscess was found in an American Bison (_Bison bison_) showing nodular precaseous tubercles of the lung. The former was the cause of death. No tubercle bacilli could be found in the abscess contents, so that the tuberculous basis is inferred, not proven. Tuberculous salpingitis in a Nylghaie was discussed on page 306.

Proboscidea. Eber mentions in the article already referred to that there are three reports in the literature of tuberculosis in elephants. When looking for an explanation of tuberculosis in this animal it must be remembered that it is one of the most attractive objects in a zoological garden and receives perhaps more attention, including feeding, from visitors than any other specimen. The beast while possessing some tissue resistance to tuberculosis, is by no means immune thereto, as has been thought by some persons on account of its reputed longevity, and therefore he is to be protected from infection just as much as other animals. It would appear that he may present caseous pneumonia or nodular caseous disseminated lesions. Our two cases, in animals at the Garden twenty and thirty-eight years respectively, were both of the fibrocaseous variety; the lesion was confined to the lungs. A brief description of their lesions is as follows:

Indian Elephant (_Elephas indicus_) ♂ . Chronic polyarthritis. Chronic myocarditis. Chronic hepatitis (cirrhosis). Parenchymatous nephritis. Chronic tuberculosis of the lungs, partly encapsulated. Pigmentation of the spleen. The pleuræ are very fat but the surfaces are smooth and devoid of adhesions. The lymph nodes of the mediastinum are about 10 × 20 cm. for the largest while the smaller ones vary around 2 × 4 cm. They are firm, deep red-brown without clear divisions into medulla and follicular cortex. There are several large, firm, pale rather cheesy follicles in all the large ones and a few of the small. These do not appear like tuberculosis. The lungs are flaccid and soft; gray and red mottled. The bronchi are firm and stand open. Around one in the upper lobe of the right lung, there is a large area of cheesy degeneration around which a zone of connective tissue has formed. This extends about the bronchus about halfway in a sheath-like manner. There is also a separate nodule the size of a cherry with a cheesy centre. The trachea appears normal. Tubercle bacilli could be demonstrated in the cheesy material. Microscopic section of lung around the cheesy area shows a low grade chronic granulation tissue in some places enclosing cheesy masses with giant cells on the margin. The neighboring septa are slightly thickened and in some places broken, forming emphysematous cavities. Some of these cavities are edematous.

Indian Elephant (_Elephas indicus_) ♀ . Miliary and conglomerate caseous tuberculosis of lung. Edema of lungs. Endarteritis deformans of lung. Cloudy swelling of liver. Chronic passive congestion of liver. Hemosiderin pigmentation of liver. Acute parenchymatous nephritis. Chronic passive congestion of spleen. Chronic hyaline perisplenitis. Multiple calcified fibroid tumors of uterus. Leiomyoma of uterine cornu. Senile atrophy of ovaries. Acute catarrhal enteritis. There are some adhesions of the upper lobes of the lung to the ribs. The lungs are large, increased in weight, color pink and mottled red, air content diminished. There are several masses of tubercles, each as large as a cocoanut, in both lobes. In one such the tubercles are yellow and caseous; some are fibroid but none are liquefied or calcified. The fibrous tissue of the lung parenchyma here is much overgrown. In one instance the terminus of a bronchus is solidly plugged by caseous material. Mucosa of bronchi is reddened, markedly ulcerated, ulcers overlaid by mucopus.

INDIVIDUAL FEATURES OF AVIAN TUBERCULOSIS.

The avian form of tuberculosis is somewhat peculiar in its physical appearance as well as in its distribution. The isolated nodular type is far and away more common by more than 100 per cent. than all the other types combined. These nodules are usually well circumscribed, and to the naked eye suggest that they have a restraining fibroid wall. This is, however, not the case, the impression being due to the dense but actively growing fibrocellular cortical zone of the tubercle. The centre of the nodule, instead of having the soft character like Camembert cheese, resembles the firm but brittle American dairy cheese. Upon opening such an area the central necrotic mass may split away from its cortex and even shell out, leaving a cavity lined by a gray-yellow membrane. These characters are best displayed in nodules of moderate size, the small ones being like the yellow mammalian analogue, the large being like indefinite cheesy masses. In the surrounding tissue evidences of inflammatory processes seem decidedly greater in our material than I am accustomed to see in human and veterinary pathology. This, it seems, should be emphasized since secondary infection with pus cocci and other pathogenic germs appears less often in birds than in mammals.

The difference speaks, therefore for a difference either in the tubercle bacillus of birds or the avian physiology. Judging by the limited morbid processes produced by injecting avian bacilli into rabbits and guinea- pigs the reaction of the bird itself would not seem wholly responsible for the difference. The local tissue reaction in all avian lesions is mononuclear and fibrous, softening and pus being rare. It would seem from this and similar operations that the bird expresses its resistance to the bacteria by a fibrocellular reaction which goes on to fibrosis without softening; perhaps this means also that their polynuclears are not sufficiently active, but the pathogenic power of the bacillus itself doubtless is individualistic.

The character of the cheesy degeneration is likewise different from the mammalian. It seems like an abrupt hyaline necrosis of a large central mass and not the slower cell death seen in the other types of tubercle. At times the degenerated area, instead of having the yellowish color of caseation, will present what we have designated “gelatinous tuberculosis,” the whole infiltrated area resembling boiled sago or tapioca. This seems to be a complete homogeneous coagulation or hyaline necrosis of the whole mass out to the delicate fibrous mantle supplied by the tissue in which the tubercle lies.

The organic distribution of tuberculous lesions has already received some attention and is to be discussed with the orders. There are, however, some localities affected conspicuously in the bird. The skin lesions often attract attention during life. They occur around the eye, at wing joints, on the cresta sterni and on the legs. Parrots and jays have shown nodular or diffuse growths around the eye, originating both in the lids and orbit, which on section have proved to be tuberculous. These seldom ulcerate, but those upon the skin of the breast and wings tend to have superficial erosions or deep ulcers. The latter lesions are more common upon pigeons but have been seen in Psittaci and Galli. Toucans and pigeons when pinioned, have on three occasions shown a tuberculous mass on the stump.

[Illustration:

FIG. 52.—MASSIVE TUBERCULOSIS IN LIVER AND SEVERAL MURAL TUBERCLES OF INTESTINE. COMMON PEA FOWL (PAVO CRISTATA). ]

[Illustration:

FIG. 53.—NODULAR HEPATIC LESIONS IN THE LIVER OF A DOVE. ]

Two parrots with hyperkeratosis of the beak and of the skin of the feet, have also had tuberculosis. These have been mentioned in literature as of tuberculous origin. One case well studied failed to show tubercle bacilli in the corns. In the absence of tubercle bacilli, one is inclined to think that this might be explained on the basis of a circulating toxin such as is assumed to be responsible for hypertrophic periosteitis. This latter condition has not been seen in birds.

Still another type of occasional occurrence deserves mention. While most of the lesions in birds correspond to the description given in the preceding pages, some lesions fail to degenerate in the centre, retaining instead a solid homogeneous fleshy character of dull gray- yellow color. Upon section these have been found wholly cellular in construction. To distinguish them from the ordinary nodules they have been designated tuberculomata. Lesions of this kind may occur along the lymphatic paths, indeed seem more common in the lateral cervical and thoracic chain, and upon bones and nerves. When they are numerous the nodular caseous type is inconspicuous. They suggest the bovine infection (Pearl disease), but one attempt to prove this failed. We are of the opinion that this is the avian lymphatic form, as our examples correspond to the literary descriptions of cervical tuberculous lymphatics in birds. No especial variety of bird is more often affected by this process.

Intestinal tuberculosis among the Aves may be said to assume three forms. The best known, indeed the form usually spoken of as representing the common picture, is that which produces varying sized nodules upon the serosa, sometimes associated with adhesions to neighboring intestines. Just how this type develops is not known. In some quarters it is believed to originate by the penetration of the tuberculous granulation tissue from the mucosa through the intestinal wall by following lymphatic channels and that irregular contractions of the musculature squeeze the exudate outward under the serosa. Other observers think that the bacilli are carried _via_ the lymphatics to the superitoneal tissue, there starting the tubercle. The truth of the matter will probably be that both methods are operative although we have seen more cases suggestive of the second than of the first explanation. When these peritoneal nodules are numerous and prominent, mucosal ulcers are uncommon and _vice versa_.

The second form is the ulcerative, flat ragged or crateriform defect situated in a diffusely thickened wall. This was well illustrated in cases of pulmonary infection in doves and guans, suggesting reinfection of the gut tract from swallowed tubercle bacilli or a backward development of the disease after the lungs were nearly solid.

The third form of tuberculous enteritis is quite interesting and striking. It is best seen in the duodenal loop but may occur anywhere. Diffuse thickening of the enteric wall is noted, and when palpation is practiced a resilient but leathery sensation is obtained. Careful inspection reveals the mucous surface to be velvety, a condition due to a swelling, that is widening, of the villi which retain their erect position and, when washed in flowing water, will be seen to move like a field of grain in a breeze. The serosa may be, usually is, negative. Studied microscopically the peculiarity of this form is in the development of tubercles and diffuse cellular exudation in the villus stalk, sometimes extending into the submucosa also. Round cell masses like lymph follicles are sometimes prominent. This form is not associated with any peculiar organic distribution so far as my studies go.

[Illustration:

FIG. 54.—TUBERCULOUS MASSES OF INTESTINAL WALL SHOWING OUTWARD GROWTH. SOMETIMES THESE MASSES OBSTRUCT THE LUMEN. ]

Passeres. The peculiarity of this order seems to be in the predominance of the pulmonary route as origin of tuberculosis. Perhaps in no other order has there been such extensive and advanced lesions as in these little birds. Sometimes one whole lung will be solid while its fellow will be half occupied by caseous material. The doves alone seem to approximate the Passeres in ability to live with so much tuberculous exudate.

Picariæ. Specimens from this order illustrate well the intestinal origin and distribution of tuberculosis. There was, among these birds, one case showing tuberculomata which was, because of its gross anatomy, listed as the pearl type. Its description is as follows:

Lesson’s Motmot (_Momotus lessoni_). The region above and behind the right clavicle in front of the brachial plexus on the internal surface of the thorax, exterior to the first and second ribs, and on the internal surface of the ribs at the junctions of ribs with the alæ of the sternum, there are many small, irregular, smooth, firm, yellowish white nodules varying in shape from spherical to sweet potato and in size from 3 × 3 mm. to 3 × 7 mm. These are found quite homogeneous on cross section. They do not resemble tubercle or mould infection but make one think of neuromata. There are also a few present in the left lateral air sacs, close to but not joining the intestine. The lungs are apparently normal. Histological section of the masses described as distributed along the nerves consist of sharply outlined but not well encapsulated masses made up of irregularly disposed bunches of large cells with vesicular nuclei in a stroma of loose connective tissue very inconspicuous in amount. There is also quite a number of small round cells and a few leucocytes. The large cells first described have the nucleus eccentric for the most part. Many of them have two nuclei and a few three and occasionally a giant cell is observed. Blood vessels have a very delicate wall and are frequently encountered in the centre of these masses. Atypical mitoses can be found. Here and there a seal ring placement of the nucleus can be found. A few eosinophiles are present not definitely placed. Necroses, with large quantities of nuclear fragments, are scattered irregularly through the mass. The diagnosis rests between an infectious granuloma, false neuroma and sarcoma. Tubercle bacilli were found by stain in great numbers both within and without the cells.

Psittaci. Tuberculosis occurs in this order somewhat more frequently in the varieties whose habitat is the Eastern world, although South American birds also suffer from it in the characteristic manner. There seems to be no difference in the pathology of these two groups. Parrots present very beautifully the separate solid or semisolid nodules of avian tuberculosis, whether they be in the lungs, liver, or spleen. When the lung becomes riddled with masses, coalescence occurs and the whole mass turns into a cast of the hemithorax. Lesions in the liver are mostly isolated, but the spleen often appears like one large pink tuberculous nodule. The liver occupies as usual the first place in organic incidence.

Striges. Owls (and Struthiones—see below) present the interesting exception to the rule of intestinal origin of tuberculosis in birds. Perhaps the platting is incorrect but the birds in the order under discussion had older and much more advanced lesions in the lungs and thoracic serosa than they did in the abdominal organs. That this was true in all three examples is in itself noteworthy. Perhaps they possess less pulmonary and more intestinal resistance. One of these birds showed a small recent cavitation in the posteroinferior angle of one lung.

Accipitres. With one exception the cases of this order occurred among the Falconidæ, that is in hawks, buzzards, and eagles. Their lesions are usually generalized as indicated by the figures for visceral distribution, but that half the number should have the oldest, most prominent lesions in the lungs is curious. Their intestinal tuberculosis seems mostly of the diffuse infiltrative type.

Columbæ. These birds are obviously the most susceptible of all the varieties of which there are sufficient autopsies to make a comparison. Generalized nodular lesions emanating from the intestinal tract comprise their usual form, while most of the hepatic lesions are small miliary and nodular; occasionally one sees caseous masses destroying large sections of the organ. Their intestinal lesions may assume any of the three forms described.

Galli. This is an order of something over the average percentage incidence for the birds but containing families that seem very susceptible to tuberculosis. The small number of Brush Turkeys (_Catheturus lathami_) had 60 per cent. of the disease, while South American Cracidæ had 44 per cent. These two groups raise the incidence for the order. Galli as a group have generalized nodular tuberculosis originating by the intestinal route. This is especially seen in the Phasianidæ, while the very susceptible Cracidæ have much more prominent lesions in the lungs, often of a massive caseous type. It is really astonishing at times how much of the pulmonary tissue is occupied by infiltrate before death has supervened.

Fulicariæ are represented by a special contingent of rails and gallinules. Avian characters are well illustrated in the order. So too the succeeding order, Alectorides, another variety of shore birds, run true to the avian form. It is interesting to note that in the two cases from each of these orders tuberculosis and aspergillosis have been combined. The former has assumed the firm nodular type, while the mycosis has been of the air sac variety. The following case is worth citing as possibly illustrating infection _per cloacam_. There is, however, no trace of this bird having been with a male with the disease.

Demoiselle Crane (_Anthropoides virgo_) ♀ . General tuberculosis including the oviduct. All organs are thickly beset by caseous tuberculous nodules except the lungs which have only a few scattered ones. The oviduct is, for its lower two-thirds, much enlarged, firm, tough, pale yellow, thickly beset with caseous nodules; upper parts uninvolved. The kidneys are definitely enlarged, irregular, almost mulberry-like, brownish yellow, firm and tough. On section the lobules are irregular, connective tissue increased, urates in pelves. Tubercles in intestines seem to be wholly peritoneal. This seems like a tuberculosis of genital origin judging from condensation of tubercles in the lower abdomen (mass around cloaca). The ovaries are not involved. Lungs and thoracic air sacs relatively free. The pericardium shows a whitish thickening of both layers due to the presence of whitish granules like urates. Histological section of kidney shows the capsule not greatly altered. Glomeruli largely negative but a few show hyaline capsular thickening of vacuoles in tufts or fibrosis in tufts or obliteration of whole structure. Tubules largely degenerated, distended or distorted. Interstitial tissue between the tubules definitely but irregularly increased. No real attempt at regeneration. Few vessels show perivascular fibrous change. One tubercle seen.

Anseres. These birds present no especial features so far as percentage or organic incidence are concerned. The individuals are mostly geese and swans, ducks being somewhat more often affected by mycosis than by tuberculosis. However, both these diseases tend to assume the nodular type in Anseres so that the diagnosis should be supported by bacteriological discovery of the respective organisms.

Struthiones. The marked feature of this order is the prominence of the isolated and confluent nodules in the lungs, of apparently greater age, certainly of great size, than similar lesions in the abdominal viscera. Caseation of the avian variety is well illustrated in these birds. The thyroid body was involved in two of the three cases, the ovary in one. The representatives of the Crypturi, two tinamous, came at the same time and lived only a few months. Miliary tuberculosis of the small precaseous variety was the form exhibited by both specimens.

HISTOLOGY OF THE TUBERCULOUS LESIONS.

The initial and characteristic unit of tuberculosis, the miliary tubercle, seems to be constructed upon the same general principles in all cases of the disease and in all members of the zoological groups in our study and in a manner entirely comparable to that well known for man and for the domestic animals. There are, however, certain minute differences which are interesting and may at some time become important. It is customary to speak of the bovine tubercle and of the human variety, but there are also slight variations of the microanatomy of each of these, while one may find on occasion a tubercle of the human type in a cow and _vice versa_. Not all the domestic animals show the bovine form, although in sheep and swine it is approximated very closely. In the horse there is much greater tendency to a central softening and fibrosis is not so common as in the bovine tubercle. I have attempted to study the histological anatomy of each of the zoological orders, but it has not resulted in any profitable discovery. It is, however, possible to contrast the type commonly found in monkeys with that characteristic for man and the ungulates and also to emphasize the construction of the avian tubercle that it may be distinguished from mammalian tuberculosis and from avian mycosis.

[Illustration:

FIG. 55. DIFFERENT VARIETIES OF THE MILIARY TUBERCLE.

A.—THE BOVINE FORM SHOWING THE NUMEROUS LANGHANS’ GIANT CELLS, THE ABUNDANT SMALL EPITHELIOID CELLS. THE MODERATE NUMBER OF SMALL ROUND CELLS, AND THE ACCOMPANYING CONNECTIVE TISSUE INCREASE. THERE IS MODERATE CASEATION. ]

[Illustration:

FIG. 55. DIFFERENT VARIETIES OF THE MILIARY TUBERCLE.

B.—THE HUMAN TUBERCLE WITH CENTRAL COMPLETE NECROSIS. TYPICAL GIANT CELLS, ABUNDANT EPITHELIOID CELLS AND THE RELATIVELY NARROW SMALL ROUND CELL MANTLE. ]

[Illustration:

FIG. 55. DIFFERENT VARIETIES OF THE MILIARY TUBERCLE.

C.—THE TUBERCLE FREQUENTLY FOUND IN MONKEY TUBERCULOSIS. WITH RAPIDLY ADVANCING CENTRAL NECROSIS ENCLOSING MUCH CHROMATIN DEBRIS. THE ABSENCE OF LANGHANS’ GIANT CELLS. THE PRESENCE OF LARGE, PALELY STAINING EPITHELIOID CELLS OF LANGHANS’ TYPE AND THE VERY SLIGHT CIRCUMFERENTIAL REACTION. ]

[Illustration:

FIG. 55. DIFFERENT VARIETIES OF THE MILIARY TUBERCLE.

D.—AN AVIAN TUBERCLE WITH CENTRAL SHARPLY MARGINATED NECROSIS CONTAINING MUCH CHROMATIN DEBRIS. THE IRREGULARLY ARRANGED POLYNUCLEAR CELLS TYPICAL OF AVIAN TUBERCLES. THE SMALL NUMBER OF REGULARLY ARRANGED EPITHELIOID CELLS. THE PAUCITY OF SMALL ROUND CELLS AND THE PRONOUNCED CONNECTIVE TISSUE MANTLE. ]

The tubercle of the Primates is a loosely constructed affair lacking the fibrous mixture of the bovine and the close cellular packing of the human form. Studied from the periphery to the centre, there will be found very little fibrocellular reaction in the immediately surrounding organ, while the mantle of round cells, rather prominent in the human tubercle, is often quite inconspicuous. The principal cellular component of the miliary granuloma is the large pale endo- or epithelioid cell, which is abundant, loosely arranged and without apparent purpose. In the centre is an irregular necrosis usually retaining some chromatic matter, probably the remains of recently destroyed nuclei, but this caseous midpoint does not assume the dense acid staining common for many milia. Giant cells of the Langhan’s or foreign body type are often entirely missing, and when present are scanty. There may be large cells, resembling the aforementioned epithelioid cells, with two or even three large palely staining nuclei, but these latter are arranged irregularly and not like the spokes of a wheel near the cell wall.

This picture suggests a rapidly growing inflammatory mass and indeed this is the type that tuberculosis follows in monkeys. In a few cases gross evidence of fibrosis in the serous surfaces and in the lungs has been observed, but they are too rare to permit one to think that connective tissue activity is an important part of the reaction of this beast to the disease.

The avian tubercle as it rests in the tissue seems like a sharply outlined almost encapsulated body. This is in part due to the homogeneity of its structure and in part to the fibrocellular condensation around the caseous part of the growths. Examined from without inward, there is a round cell mantle, between the elements of which course fine but easily perceptible fibrils; elastic tissue has been seen among them. The small cells continue more deeply than the fibres, to be succeeded in prominence by epithelioid cells of rather dense character, the nuclei especially seeming quite rich in chromatin and round. The rotundity of the nuclei remains not only in the single separate cells forming the middle zone of the cellular cortex, but can be found in the nuclei of the compound or giant cells which comprise the internal layer lying upon the necrotic centre. These giant cells are characteristic for the avian tubercle in assuming a form like syncytia with nuclei arranged in irregular radiating columns. This internal large cell area may completely surround the central necrosis or it may be interrupted by the large single cells. Tubercle bacilli are more common in and between single cells than multinuclear ones. Within the cellular zone lies the necrotic centre, often, indeed usually, full of chromatic debris. This centre is commonly quite amorphous but occasionally one will see what is probably the remains of a coarse coagulum. Between the necrosis and the cells one usually finds a split, a sort of separation of the gangrenous from the living part. Old tubercles with denser fibrous capsule retain this microanatomy in part, but the cellular zone gradually becomes thinner and thinner until all that remains is a narrow cortex of round cells and imperfectly retained multinuclear cells.

Tuberculous granulation tissue without definite milia consists entirely of the round cells with small vacuoles and a fine but definite fibrosis. Tuberculomata consist of cells of varying sizes with small round nuclei. Interstitial fibrosis is delicate and barely visible unless especially sought. Giant cells may be encountered but are not so large as in milia. Necrosis occurs but not in an orderly manner in relation to cells as in an isolated tubercle. Tubercle bacilli are very numerous.

[Illustration:

FIG. 56.—PHOTOGRAPH OF YOUNGEST AVIAN TUBERCLE AFTER COMPLETE FORMATION. ]

[Illustration:

FIG. 57.—TUBERCULOMA, A SOLID TUMOR-LIKE MASS, CONSISTING OF CLOSELY PACKED LARGE CELLS FITTED WITH RELATIVELY SMALL ROUND LOOSE NUCLEI. THESE CELLS ARE CROWDED WITH BACILLI. ]

TYPES OF BACILLARY INFECTION.

According to experimental and statistical research, all the tubercle bacilli of the higher vertebrate classes can be infective for any member of these classes. Thus, for example, human bacilli have been found in many orders of mammalia and in birds. The bovine form has been found in swine. The lesson from this is that while the special predilection of a variety of the tubercle bacillus may be for one kind of animal, it is potentially a virus for other kinds. Hygienic principles have therefore been laid down at the Garden which aim at the protection of all specimens from every variety of tubercle bacillus. For this reason and because the laboratory has not attempted extensive research on bacteriology, few type determinations have been made and those at hand offer nothing new or unusual; they are noted here as a matter of record. Bovine bacilli have been judged by their slow growth and infectivity for rabbits, human bacilli by the reverse of these characters. Avian tubercle bacilli can be cultivated with reasonable ease directly from lesions not bearing a mixed bacterial flora, and grow in a yellow, moist, even, spreading colonization. In our two attempts at infection of guinea-pigs, no success was had, although Rabinowitsch and others had no difficulty in so doing; this strain may vary in virulence as do other tubercle bacilli. No avian culture was obtained from a mammal, but a bovine was found in a parrot and a human in a duck. Bovine bacilli were isolated once from a monkey (see page 496) and in another case of lymphatic type, bacilli of the short heavy blunt shape, supposed to be characteristic of this variety of the germ, could be stained. Monkey tuberculosis in our experience is usually due to the human tubercle bacillus, judging by the staining characters and two successful cultures.

DISCOVERY OF TUBERCULOSIS DURING LIFE.

Fully developed chronic tuberculosis may be recognized with reasonable ease in the human being and some domestic animals. The diagnosis rests largely upon the history and symptoms and partly upon the appearance of the individual and upon signs elicited by physical examination. There is good reason to believe that these latter methods are entirely applicable to certain wild animals, notably those that can be caught and held quiet, but because of their naturally great reserve many specimens offer little reason for suspicion as to their tuberculous condition until near death. Certain ungulates with chronic pulmonary disease get thin and weak but remain on their feet with good appetite and satisfactory discharges for many months. Primates, Carnivora, Rodentia and Aves not uncommonly come to autopsy with very good coats and without great emaciation and yet are heavily infected. It can be stated with fair positiveness that no chain of historical data or gross observations are certainly known to us as indicative of tuberculosis in the wild beast. Coughing is not necessarily characteristic of chronic pulmonary infection, although when continuous it rouses considerable suspicion, especially in the Ungulata. It is to be interpreted with care in all animals that have loose bedding as bits of straw or seeds get into the throat causing irritation; the dust of hay may cause coughing in horses.

However much chronic or fatal tuberculosis may be interesting from the standpoint of pathology or of zoological or visceral incidence, the most important factors in our knowledge of the disease are its early recognition and treatment, either for curative or hygienic purposes. Since we have learned that advanced lesions may exist in an animal without materially affecting its external appearance and behavior, it naturally follows that early cases, possibly of an “open” or infectious character are still less likely to give evidence of their existence. This is well recognized by veterinarians as being true of cattle, but is perhaps less well known, or possibly admitted, by those who handle the very susceptible monkey.

Upon a visit to a foreign garden I was told that experience alone is sufficient to enable an observer to detect tuberculosis, and that the disturbance entailed in physical examination and tuberculin tests is prejudicial to the well-being of all varieties, but especially the delicate ones. I learned later that they had the disease in their exhibition cages all the time but decided to put their method to the test. Shortly after my return from abroad a splendid specimen of Grivet Monkey (_Cercopithecus sabæus_) was condemned by the tuberculin test. He was well studied by the superintendent and two very experienced keepers, all of whom pronounced him one of the finest specimens they had ever seen, and stated that he was behaving quite normally. Despite their protests he was sacrificed, tuberculosis with early cavitation being found in the upper lobe of the left lung. Incidentally vague physical signs were found by auscultation, but as the monkey was unruly and had long pectoral hairs little weight was placed on the observation. However, it is frequently possible to make very thorough physical examination of the lungs of the more tractable specimens, diagnoses of pneumonia and bronchitis being frequently made in this and other parks, so that treatment may be instituted.

IMPORTANCE OF TRANSMISSION AND KNOWN SUSCEPTIBILITY.

Some light upon possible reasons for the poor condition of an individual animal is of course shed by a knowledge of the disease to which that particular variety is most susceptible, to which may be added the data obtained from previous deaths in the same group or enclosure. Thus, for example, a sickly monkey would be suspected of having tuberculosis or early osteomalacia, whereas no suspicion of these diseases would fall upon the marsupials. The same position would be assumed if a dove and a heron were out of condition.

In so far as enclosures are concerned, the matter is somewhat different. Whenever a case of tuberculosis occurs in a cage, the remaining specimens if any are removed and the place cleaned by soap and water and disinfectant and paint. The naked flame from a blast lamp is used when possible. Out-of-doors enclosures are vacated, spread with lime and allowed to lie fallow for as long a time as practicable. These methods have been in the main successful in clearing a cage of the disease, and all our experience demonstrates the effect of cage hygiene and the selection of non-infective replacements. A few places such as those occupied by doves and guans have not been freed of infection, if one judge by its appearance when new specimens are placed in them, but they may of course be due to the infection from elsewhere. The history of seven years in the new bird house where the hygienic conditions are excellent, seems to indicate that a cage thoroughly cleaned is no longer a source of danger, and that a repetition of tuberculosis in such an enclosure is due to its importation with new exhibits.

The spread of the disease to nearby cages seems to depend upon two factors. If the number of cases has been large and the infection virulent, immediately adjoining cages are involved, but the tendency to spread is directly proportional to the proximity of orders or families that have a high susceptibility for tuberculosis. This second factor seems to be the more important and is illustrated by our experience in one corner of the new bird house. In this area are exhibited certain doves and pheasants, among which are many cases, while the passerine varieties nearby are little affected. So too in the flying cage the disease has occurred in varieties with high general susceptibility. There are at the present writing ten orders on exhibition in this large enclosure and there have been more. An occasional case of the disease occurs, but only in the orders which show it elsewhere. The Herodiones, of which we have had nearly one hundred autopsies and many now are on exhibition, are always well represented in this cage and yet show no tuberculosis. In the ten orders mentioned above three show no cases of the disease.

These observations illustrate the spread of tuberculosis, especially to the most susceptible varieties, and how non-susceptibles under good hygienic conditions fail to become infected even when infected animals are near them. The freedom of activity in the large enclosure is doubtless an important factor.

The history of the past three years with regard to the control of tuberculosis in the small cages shows that twenty-nine were infected, but by the measures employed nineteen have remained free of the disease for one year; three of the remaining ten are known to have received newly arrived and possibly infected specimens.

The accredited method of transmission in birds, the swallowing of material soiled with the feces richly laden with germs, is the principal reason why infected enclosures and their immediate environment are the principal breeding places for tuberculosis. To be sure air currents may blow the virus around, allowing it to light upon food in other cages but this cannot be a great menace if for no other reason than that we have had no epizoötic outbreak of the disease, when there were groups of deaths in doves and guans.

Evidences with which to trace transmissions are much clearer in the birds than in the mammals with the exception of monkeys and some ungulates. Of course cases are perhaps too few in the carnivores and rodents to permit correct deductions but it is very rare that more than one case occurs in the same enclosure containing groups of these varieties. Nor do animals in adjoining cages seem to “catch” the infection. This observation does not suggest that any relaxation of hygiene need be allowed but probably it implies that not many bacilli are excreted by these animals; they cough very rarely. Groups of ungulates (bison and deer) are often known to be infected but just how it has arisen is seldom clear. Transmission from monkey to monkey has been observed so frequently that it cannot be doubted, nor will anyone wonder at it if reflection is given to the close personal contact of these animals during their natural behavior. They huddle, pluck lice from one another, take food from the mouth of another, bite and perform many other actions greatly facilitating the transfer of any virus. Bacilli may also be disseminated by coughing, drooling and with the fecal discharges, for which latter there seems ample opportunity since a notable percentage of cases have intestinal lesions. Monkeys do not seem to raise sputum and expectorate it but they do eject saliva from their lips.

Contraction of the disease from infected cages is believed to have occurred at least once in our experience but the lesson of complete sanitary cleaning of the enclosure learned from that happening, seems to have enabled us to forestall its repetition.

THE TUBERCULIN TEST.

Tuberculosis presents the greatest single problem among the specific infectious diseases which the director of a menagerie must attempt to solve. Even though one may possess a knowledge of its zoological distribution, clinical characters and pathological effects, these are insufficient criteria for its detection at a stage when the animal might be saved by treatment or, what is most important, removed from its companions that they might be protected. To this end there remains but a single procedure for the discovery of the existence of tuberculosis—the use of tuberculin in one of its forms by one of its methods of application. The use of this test in veterinary medicine needs no commentary, having made its place in clinical and hygienic practice for a quarter century or more. Armed with the knowledge of the satisfactory use of the toxins of tubercle bacillus in cows, Dr. Penrose, Dr. C. Y. White, Dr. A. E. Brown and Dr. Leonard Pearson began in 1901 a series of experiments with old tuberculin of Koch which have led to the development of a technique for its use in the detection of infected monkeys. These interesting and instructive animals, being known as highly susceptible since most of the collection died of the disease in those days, and being handled with reasonable ease by experienced men, were investigated as the most important specimens upon which to perfect the method. Other varieties have been studied since and I shall refer to them individually. The greatest amount of work and the most conspicuous success attended the observations upon monkeys and the results of this study are now in daily use in this Garden.

The work, conclusions and results, originated by Doctor Penrose, Doctor White, and Doctor Brown can be described as one of the most completely satisfactory series of observations in scientific medicine. Applying the principle that a tuberculous animal reacts to the injection of tuberculin by a temperature rise, the normal temperature curve of the monkey was studied, that of the tuberculous monkey determined by killing many specimens. This enabled them to state which animal was infected, which was not and to place on exhibition only healthy specimens. Added to this, strict hygienic principles in the housing and handling of the animals have resulted in the elimination of the disease from our exhibition house. Occasionally a case may develop, perhaps from feeding by visitors, but the matter is no longer a problem. I know of no more complete and satisfactory experiment and its practical application than this work, which is condensed in the succeeding paragraphs.[101]

THE TEMPERATURE OF MONKEYS.

The success of the tuberculin test in the lower animals as in man depends chiefly upon the alterations in temperature following the injection of the toxin. It is generally admitted to-day that a healthy animal’s temperature will not be affected by the introduction of this material. There are in addition changes in the pulse and respiration rate and in the physical signs but these are detected with difficulty and are much less definite than thermometric records. The first essential was therefore a thorough familiarity with the normal temperature of the monkey, a requirement which met with considerable difficulty from the beginning since the earliest observations revealed puzzling irregularities. This necessitated the establishment of certain regulations of technique which, after the preliminary tests, have been found satisfactory enough to continue until the present day. All monkeys are received in the quarantine rooms of the laboratory where they are observed by the officials of the Garden and of the laboratory and there they remain in separate cages until passed, as free from tuberculosis, to the exhibition house.

The handling of monkeys for the purpose of taking temperatures is a matter of no small importance since excitement will quite definitely increase the registration. We have been fortunate enough to have in charge of this work since its inception the same man, Keeper McCrosson, who is thoroughly experienced in the care of these beasts and who can catch and hold them with a minimum of disturbance. To him and to the interested laboratory helpers much credit is due. Small specimens like capucins and spider monkeys are caught with the gloved hand or with the protection of a piece of heavy cloth. Larger specimens may be caught in a net while strong monkeys are fitted with a collar and chain by which they are pulled into the corner of the cage and held, while the door is opened to permit a helper to catch the feet and arms. Two experienced men can take the temperature of any monkey that can be handled at all safely. The knowledge of how to do such work reduces the excitement of the animal and renders more accurate the observation of its temperature. During the period of temperature-taking food is given in small quantities and only after the record is made.

Temperatures are taken in all animals by rectum,[102] the thermometer, a separate instrument but always the same for each animal, well greased with plain vaseline, being passed along the anterior rectal wall and allowed to register for twice its indicated speed. During the preliminary work, special instruments of officially standardized accuracy were obtained by Doctor Brown but once the normals were obtained, ordinary good thermometers registering from 94°F. to 108°F. have been employed. If the record vary very much from the expected, such as the figures obtained at the same time on the preceding day, or if the rectum be crowded with feces, the instrument is shaken down and reintroduced. In order to facilitate timing of exposures we use sand glasses of three minute run.

After some experimentation by taking records at various times of day it was found that monkeys as a group do not have a uniform temperature during twenty-four hours but register a higher figure during daylight than during darkness. This is probably due, as I shall discuss, to the period of activity, not to the time of day. Figures obtained at various hours indicated that the highest and lowest temperature would be obtained if records were made at four-hour intervals at three, seven and eleven o’clock AM. and PM. To give the normal temperature of a monkey, the kind and the time of day are necessary adjuncts. Reference to forty- eight hour charts which are used for the illustration of normal records, and for contrast with tuberculin reactions later, will convey to the reader a better idea of the normal daily rhythm of the simian heat regulating system than would verbal description.

[Illustration:

CHART A. ORANG UTAN (Simia satyrus). Non-tuberculous at death. ]

NOTE.—In the temperature charts degrees indicated by circles and connected by dashes are from records made after diagnostic tests by injecting tuberculin.

The anthropoid apes (Curves A and B) have on the whole a mean temperature nearer the human being than do the lower monkeys, but they too present daily variables far greater than man. The high point of their curve, at three PM., is in the neighborhood of 100°F. the lower point around 97.5°F. From these charts and other records it can be said that while the higher apes have a daily temperature curve with its high point at three PM. and its low point at three AM., there is in them not by any means the regularity of curve to be found in Cercopithecidæ and Cebidæ. Our records of temperatures in the Hylobates (_Gibbons_) are not extensive enough to quote but what we have approach those of the lower monkeys.

[Illustration:

CHART B. CHIMPANZEE (Pan niger). Non-tuberculous at death. ]

Graphic curves of the normal temperatures of the various genera of Cercopithecidæ and Cebidæ present striking similarities in the regularity with which the daily rhythm is performed. In the seven genera of which we have accurate records the normal high points fall between 102°–103°F. and the low points between 99°–100°F. while the curve of the four-hourly steps is closely comparable. The curves D to J are composites from charts of animals that have been tested with tuberculin, which thereafter died or were killed and found free from tuberculosis. Not every individual chart that may come to hand necessarily follows the exact course detailed in these illustrative curves but these latter offer a guide as to what is to be expected of the different varieties. They show unequivocally the V-shaped curve of the temperature of the monkey during twenty-four hours.

[Illustration:

CHART C. Composite chart of twenty-two non-tuberculous Lemures. ]

The Callitrichidæ or Hapalidæ have failed to show tuberculosis in our Garden and little has been done upon them. As a matter of record there is reproduced the only satisfactory chart at hand (K) taken very early in the researches. It shows a similarity to those of the higher monkeys; because of its very high afternoon record the animal was killed; no tuberculosis was found.

[Illustration:

CHART D. Composite chart of eighteen non-tuberculous Cercopithecus. ]

The Lemures, being close to the Primates zoologically and presenting a high incidence of tuberculosis, were included in this study. Observations upon their normal temperature were hampered more than upon that of monkeys and even to-day we cannot feel the same confidence in the records. Irregularity is most marked and they seem easily disturbed by handling. Chart C shows a composite temperature for forty-eight hours of twenty-two proven non-tuberculous Lemures. The tendency for the “night drop” is certainly existent but with much less definiteness than in the Primates.

CONDITIONS WHICH MODIFY THE TEMPERATURE.

[Illustration:

CHART E. Composite chart of seventeen non-tuberculous Macacus. ]

Observations by A. E. Brown[103] and by Simpson and Galbraith[104] would seem to indicate that the diurnal variation in monkeys is due to periodicity of activity. Doctor Brown found that the temperature of a night monkey is reversed, that it is higher during the dark than the daylight hours. See chart of Potto (_Perodictus potto_) chart L. The Scotch observers report that if the activity of day monkeys were reversed, daytime being made artificially dark and activity forced during the night, the temperature curves were likewise reversed.

[Illustration:

CHART F. Composite chart of eleven non-tuberculous Papio. ]

Perhaps the most important discoveries of these investigators concerned the influence of excitement upon the temperature records. These observers indicate definitely that the greater the physical activity and nervous excitement the higher the thermometric record. We have noted that the substitution of a strange keeper who may not be gentle and tactful with the monkeys can serve to raise the temperature above the records obtained by an experienced man with whose methods the animals are familiar.

A knowledge of these facts dictates at least two important precautions on our part—our specimens must be kept under identic conditions peculiar to their kind, and surroundings must be established offering comfort with a minimum of annoyance in transfer and handling. To this end all specimens upon receipt are put into separate cages suitable to their size and allowed to become accustomed to their surroundings for several days before attempt at temperature-taking is made. Mention has already been made of the experience and interest of the principal keeper; the regularity of records is an attest to his work. Daily three o’clock afternoon temperatures are taken first to accustom the animal to the matter, before test records or tuberculin injections are made.

The existence of pathological states undoubtedly affects normal temperature curves and tuberculin reactions. Gastroenteritis has the effect of increasing the whole level and of making irregular the midday and afternoon records. Respiratory tract disease cannot be said to have a very definite effect; its most frequent influence seems to be to drive the night records lower so that there is a long fall between seven and eleven PM. and a long rise between seven and eleven AM.

THE TEST.

The preliminary rest of the new arrivals having passed daily three o’clock afternoon temperatures are taken until an even level is obtained; this requires usually four days but in very nervous specimens it may be much longer. The afternoon temperature course provides not only a means of teaching the monkey what is coming but supplies us with a high point record for comparison. When a new variety is received, a full normal twenty-four hour record is usually made. This preparatory routine being fulfilled, the animal is injected under the skin of the thigh or flank with freshly diluted mixed bovine and human tuberculin.

THE DOSAGE.

Early trials with this substance revealed the fact that a dosage based upon the weight in comparison to man failed to elicit a definite response whereas if based upon relative weight of cow was too large. The finally determined quantity was arrived at, as was the case in early human and bovine work, by experiment and trial and was as follows: A monkey of five to ten pounds (2.3 to 4.5 kilos) received an initial dose of 1. milligram and for each additional five pounds (2.3 kilos) 0.5 mg.; this is 0.2 to 0.4 mg. per kilo. The amount given to man varies from 2. to 5. mg.; if the body weigh 60 kilos this is 0.03 to 0.08 mg. per kilo. Cows are given usually in this country 400 mg. or, for a cow of 250 kilos, 1.6 mg. per kilo. In the early work, doses comparable to the figure for man failed, whereas at least two animals died very quickly after 1.+ mg. per kilo; 5. mg. was the original high dose. While the death of a monkey after a large dose was of no moment and was perhaps desirable, it would only be the heavily diseased specimens and this would give no criterion upon which to judge the appropriate dose for all. Experience seems to warrant us in continuing with our present figures since all tuberculous monkeys have reacted to it. Subsequent cases for retest are increased from 50 to 100 per cent. depending upon the size of the monkey, the very robust and vigorous ones receiving an increase represented by the higher figure. One monkey injected eight times has risen from 1. to 24. mg. with constantly a negative response over a period of nine years.

Doses for Lemures are relatively higher, averaging 1.5 mg. or about 0.5 mg. per kilo; they are increased in the same manner as above.

THE TEMPERATURE TAKING.

Injections are usually made in the late forenoon, temperature records being started at the usual three PM. hour and continued at four-hour intervals for forty-eight hours, giving thirteen records over two days, a time period presenting two complete cycles of diurnal variation. This was found necessary because certain cases do not react during the first day. Explanation of this was sought in the nature of the lesion but could not be found further than that mild early lesions may give it but it cannot be read as indicative of low activity since one case of laryngeal tuberculosis had this “delayed reaction.” At times it has seemed to occur when the injection fluid formed a blister under the skin, a pocket in the areolar subcutaneous tissue, whence absorption would be slow. Whatever the correct explanation, experience has justified the recording of temperatures for full forty-eight hours.

[Illustration:

CHART G. Composite chart of five non-tuberculous Cynopithecus. ]

[Illustration:

CHART H. Composite chart of eleven non-tuberculous Ateles. ]

THE REACTION.

The experience gained with these monkeys supported definitely the general opinion that tuberculin injected into healthy animals will not disturb the temperature but will produce decided changes in that of tuberculous animals. The reaction in the tuberculous animals may assume several characters, of which usually two are combined in a chart. The commonest and most convincing is a definite rise in the first twelve hours, amounting to one degree or more; rarely it may be three degrees (W). This is followed either by a maintenance of a high level or an attempt to perform the night drop. It may be said that in general there is an abortive attempt in nearly all tuberculin reactions to simulate the V of the normal cycle; this can be seen in charts M, N, O and P. Another rise may be attempted during a similar period of the second twenty-four hours or the whole course may at that time approximate the normal. A modification of this type of reaction is the performance of the whole daily rhythm on a high level, set, as it were, by the initial three PM. record. This form is confusing at times and has been responsible for at least one of our mistakes. Combined with this high level of curve is a tendency for the second twenty-four hours to be higher than the first day (See Variegated Cebus Q and Sooty Mangabey R and Chacma Baboon W). The second type of reaction, illustrated by chart S, fails to resemble the normal daily cycle of the monkey temperature but has sudden rises and falls as its characteristic feature. We have learned to look with suspicion on all charts with sudden marked changes of record even if they follow in the main a rhythmic course. The sudden fall exhibited by a very sick monkey illustrated by Grivet Monkey (T) and Campbell’s Monkey (U) is a bad sign. It has been met more often in advanced caseous pulmonary tuberculosis than in any other tuberculous lesion. On two occasions it has been seen in the absence of tuberculosis so that retest is indicated if the specimen be valuable; such animals however rarely survive the disturbance incident to the test as they are usually suffering with some serious disease. Illustrative charts of several positive reactions serve to elucidate their character better than description. If comparison and contrast of the normal and post- injectional temperature be made, the conclusions are definite.

[Illustration:

CHART I. Composite chart of eight non-tuberculous Cercocebus. ]

[Illustration:

CHART J. Composite chart of twenty non-tuberculous Cebus. ]

It cannot be said that any type of reaction indicates a particular form of disease although the last type, the falling of the temperature beyond the thermometric registration point, usually means advanced lesions especially of the caseous pneumonic form. A very small lesion may give a definite reaction as in Cebus (V).

[Illustration:

CHART K. GEOFFROY’S MARMOSET (Leontocebus geoffroyi). Non-tuberculous. ]

The examples given are those of a definite character but there are many charts that vary from the normal upon which a decision is extremely difficult to make. Such animals are held in quarantine to be retested after the lapse of three months. Early in the work a suspected specimen was reinjected after two weeks, failed to give a reaction but died in about two months of tuberculosis. The nullification of the test by previous injections of tuberculin is well known. Three months’ interval permits a disappearance of the non-sensitivity and allows any latent tuberculosis, possibly stimulated by the toxin, to develop. Repetition upon the same monkey has occurred as high as ten times without apparent harm.

[Illustration:

CHART L. POTTO (Perodicticus potto). Healthy. ]

There are sometimes in human beings local reactions at the point of injections. These have been entirely lacking from our monkey specimens. Nor have we ever seen secondary tuberculous lesions appear at the point of the needle-stick. Aseptic syringes and generally cleanly technique have also protected against local abscesses. When an animal is injected he may scratch or pick at the spot for a minute or two but thereafter seems to ignore it entirely.

[Illustration:

CHART M. MONGOOSE LEMUR (Lemur mongoz). Tuberculous. ]

[Illustration:

CHART N. BLACK HANDED SPIDER MONKEY (Ateles geoffroyi). Tuberculous. ]

RESULTS.

The value of the test can best be estimated by a recital of the mortality of monkeys, from tuberculosis, since its inception. Before the test was started practically every monkey in the collection for sufficient length of time to be exposed died from the disease. The average duration of exhibition life of all specimens up to 1903 did not exceed eleven months. The time has risen almost uninterruptedly until now it is thirty-five months. There are, at time of writing, sixty-eight specimens in the cages which have been on view from one to one hundred and eighty-five months with an average of fifty-four months. These figures speak for themselves as evidence of the reduction of infection. The average mortality from enteritis and degenerative bone disease has remained about the same through all these years. Percentage figures such as are recorded in our yearly report are misleading because all monkeys written into the property record of the Garden are listed and since some of these specimens remain in quarantine, they do not properly belong to the exhibition collection. Up to 1906 when the test technique was perfected nearly all deaths were due to tuberculosis, the figure for 1906 (including experimental animals) being 78 per cent. However from February 1906 to October 1907 and from then until May 1910 no case of tuberculosis occurred in the exhibition cages and both deaths at these given times seem like infection from visitors. During the next three years thirteen monkeys died of the disease in the exhibition and many more in quarantine. By 1913 the outbreak was stamped out. Its explanation is not so very far to seek. In the fall of 1910 we obtained some suspected monkeys which were kept in one of the quarantine rooms. After repeated testing two were passed. From them five cases are known to have originated and it was not until in 1912 when the whole exhibition house was cleaned of specimens, thoroughly disinfected and fumigated and until every specimen was retested, that the infection passed. In 1914 no cases occurred, while in 1915 a case either slipped through undetected or was a visitor infection; 1916 two cases, 1917 one case, 1918 one case (see orangutan charts), 1919 and 1920 none and 1921 one case, 1922 no cases. Since 1912 the whole monkey collection has been tested every two years, a method which enabled us to catch a small group in 1916 and has protected the collection since then. Three of the six monkeys specified above were never placed free in the general cages of the exhibition house, they being segregated in smaller cages. One, the orang, was with its mate in an isolated cage. The other two were in larger cages and their history suggests visitor infections.

[Illustration:

CHART O. RHESUS MACAQUE (Macacus rhesus). Tuberculous. ]

[Illustration:

CHART P. ORANG UTAN (Simia satyrus). Tuberculous. ]

We have never underestimated the possibility that an occasional very early case might evade detection by this test but we believe the history just outlined warrants us in depending upon it for the protection of the exhibition. By the tuberculin test we have detected the existence of the disease in twenty-three per cent. of specimens. Every condemned specimen, forty-one, showing tuberculosis, gave a positive test. Fifteen monkeys condemned on their temperature charts failed to show the disease. Eight per cent. of the tests resulted in suspicious charts, and the animals finally died of the disease in quarantine. Fifty-six tuberculous monkeys died on exhibition, of which thirty-one were original there and twenty-five their contacts. Twelve of the thirty-one were in the early stages of the work, thirteen due to our misadventure of 1910 and the remainder, six, scattered over nine years.

[Illustration:

CHART Q. VARIEGATED CEBUS (Cebus variegatus). Tuberculous. ]

[Illustration:

CHART R. SOOTY MANGABEY (Cercocebus fuliginosus). Tuberculous. ]

Another interesting experience concerns the exhibition of a group of Rhesus Macaques in an open “band stand” cage. The idea arose in an attempt to find a separate exhibition space for some good specimens that gave unsatisfactory charts, with the purpose of applying at the same time the “open air” treatment if tuberculosis existed. The experiment has been entirely successful since in the eleven years during which this enclosure has been used there has been but a single case of tuberculosis among twenty-six monkeys. Curiously enough this exception gave a good chart and we suspect it was a visitor infection; no secondary case arose from it. The animals housed in this cage keep in excellent condition, their coats responding to our severe winter by increasing in thickness and glossiness. Frozen toes, fingers and tails are sometimes seen but these monkeys seem just as happy as the others. Breeding is active and the young are lusty and husky. Practically the only deaths are due to accident, or to abuse of old and less vigorous members of the colony. We are unable to give comparative exhibition periods and death rates for monkeys in the large house and this open cage because some specimens have been changed from one to the other but it is certain that the appearance of the “band stand” monkeys is better than those in the house and there are four of eleven animals in the former which have been there eleven years and only four among the seventy in the exhibition house for that length of time.

[Illustration:

CHART S. VERVET MONKEY (Cercopithecus lalandii). Tuberculous. ]

[Illustration:

CHART T. GRIVET MONKEY (Cercopithecus sabæus). Tuberculous. ]

The results of the foregoing work seem to demonstrate that the tuberculin test permits the separation of tuberculous and non- tuberculous monkeys and that its employment serves the purpose of maintaining a healthy exhibition by excluding infected specimens. These experiences form further corroboration of the facts that tuberculosis begets tuberculosis, that a healthy individual is not a source of infection. It follows that an obviously tuberculous animal should not, need not, be a source of danger; the hidden or unrecognized case is the menace. There is little or no problem when an unequivocally good or bad temperature record is obtained; it is when there are slight variations from the standard for the group that decision as to the disposition of the specimen must be made. Nearly always such specimens are retested until the records are definite. If they be constantly irregular the animal is either sacrificed or exhibited in a separate cage far from other monkeys. It is by the sacrificing of infected specimens or the segregation of suspected ones that our collection is kept clear of disease.

[Illustration:

CHART U. CAMPBELL’S MONKEY (Cercopithecus campbelli). Non-tuberculous. (See page 533). ]

Hygiene of a general character must be maintained also. Our quarantine rooms are disinfected by formaldehyde and mechanical cleansing after every case detected as tuberculosis, and painted every two years. Monkeys associated with infected ones, are retested and then given a bath of carbolized water before being put on exhibition. The exhibition house is mechanically and chemically disinfected at the injection time each two years. All keepers are examined for tuberculosis upon beginning their employment and those handling monkeys, periodically thereafter. When a case of tuberculosis dies, all animals in the same and adjoining cages are removed for retest and the enclosure scrubbed and disinfected.

[Illustration:

CHART V. WEEPER CEBUS (Cebus capucinus). Tuberculous. ]

There is a source of tuberculosis upon the importance of which we can only speculate—the visitor. There were two isolated cases in animals which had passed the test with unexceptionable charts, three and four months on exhibition; curiously enough no other cases occurred in their cages. These we have laid to visitor infection since no previous exposure can be traced for the specimens and no secondary cases occurred.

I can conclude this discussion of the tuberculin test and of the control of tuberculosis by its use, by mentioning the possibilities for the solution of the problem in man. While the eradication of the disease cannot be accomplished as easily as if a potential source could be eliminated by sacrifice, it will come in direct relation to the earliness of detection of infection and isolation of the sources of danger. Not so much the cough-racked consumptive but the unrecognized early lesion whose bearer hawks and spits in public places or at home, unaware of his malign power!

[Illustration:

CHART W. CHACMA BABOON (Papio porcarius). Tuberculous. ]

THE SKIN AND EYE TESTS WITH TUBERCULIN.

The first of these can be dismissed briefly, for in a few cases it was absolutely of no value. A known tuberculous monkey was injected _into_ the skin of the chest with 0.5 mg. of old tuberculin. The small bleb disappeared in a few hours and was followed by no reaction whatsoever. Other attempts likewise failed, some of them I believe due to the technical difficulty of injecting into the skin. This tissue is very thin, delicate and loose at the less hairy places where a reaction might be read—arm, chest, abdomen. The hairless parts of the rump might be used, but are so often scratched and soiled with dirt that readings might be misleading. The Von Pirquet test was done on the first mentioned specimen and was likewise negative. His tuberculin test was afterward positive.

[Illustration:

CHART X. BLACK APE (Cynopithecus niger). Tuberculous. ]

The ophthalmic reaction is highly spoken of in the New York Zoological Park and has been used elsewhere. It was tried by me at the time Doctor Blair first discussed it, but with variable results. One set of two monkeys was treated with Calmette’s purified tuberculin into the conjunctival sac and given a subcutaneous dose of old tuberculin. Another set received 1 per cent. old tuberculin into the conjunctivæ and the usual subcutaneous dose. Although all these monkeys gave a temperature reaction only one gave a conjunctival reaction. Fearing that the two tests simultaneously might be an unfair trial, another poor specimen was given an eye test which resulted negatively; a later subcutaneous test and autopsy revealed the disease. Because of these experiences and the fear that any reacting conjunctivæ might become secondarily infected from the uncertain personal hygiene of the beast, we decided to omit this method and rely upon the temperature test.

PATHOLOGICAL EFFECTS OF THE INJECTION OF TUBERCULIN.

It is generally believed that tuberculin injected into tuberculous animals, in doses large enough to produce a marked reaction at the site of disease, may stimulate the process to growth and spread and that certain parenchymatous organs in such bodies undergo degenerative changes. We can give little information concerning the first point because known infected animals have not been sacrificed during the test and we are not informed of the degree of morbid lesion in those dying, since we had no previous knowledge of its existence.

[Illustration:

FIG. 58.—EFFECT OF TUBERCULIN ON THE KIDNEY. AN UNUSUALLY SEVERE REACTION IN THE RENAL TUBULES AND INTERSTITIAL TISSUE FOLLOWING A TEST DOSE OF TUBERCULIN. SUCH A MARKED CHANGE SUGGESTS THAT IN THIS CASE PRE-EXISTING RENAL DAMAGE WAS AGGRAVATED. THE ANIMAL WAS TUBERCULOUS BUT HAD NO LESIONS IN THE KIDNEY. ]

An interesting and practically useful observation has, however, been made upon the kidneys of several monkeys dying shortly after tuberculin injection. It consists in a marked cloudy swelling of the renal epithelium and a congestion or even thrombosis of the glomerular capillaries, accompanied sometimes by increase of nuclei in the tuft and by amorphous material in the space of Bowman. Grossly such kidneys are but little changed, albeit the cortical zone may be dull and opaque and swell out slightly on section; very occasionally bloody streaks may separate the cortical and medullary striæ. In a few kidneys there have been suggestions of preëxisting nephritis but usually the findings are confined to those given above. At all events true glomerulonephritis is not often found. Monkeys which have this condition may or may not exhibit a behavior suggesting its existence. Sometimes it will be noted that the animal is dull and eats little, at other times the keeper will report that the cage is seldom wetted and we know of cases in which only an ounce or two of urine has been passed in a day. Two monkeys were distinctly ataxic and incoördinate and one of these had a convulsion. From one a specimen of urine showed albumen but no casts.

These signs of renal affection are not always alone nor are the kidneys necessarily the only part diseased since postmortem records show a variety of accompanying lesions, bronchitis and enteritis, for example. There are, however, several cases dying in a few days after tuberculin injection, both with and without tuberculosis, in which the renal changes were quite prominent; two examples, without tuberculosis, exhibited the damage to the kidneys very well and with no other evident visceral pathology. The relation of cause and effect may not be unequivocal, but these findings suggest that the condition of the kidneys deserves attention when tuberculin is to be injected. My associate, Dr. Corson-White, is firmly convinced that the substance whips up a preëxistent parenchymatous disease and wants to see a urinalysis from every monkey that is in any way abnormal.

THE TUBERCULIN TEST IN OTHER ANIMALS.

Two cases of tuberculosis occurred in White nosed Coatis (_Nasua narica_) so that it was decided to test their neighbors in the next cage. There is reproduced a composite (Y) of the temperature record of three of these animals after receiving 2 mg. of tuberculin under the skin. No tuberculosis was found in them at death, all dying within two years. The similarity to the primate type of temperature curve is striking.

Chart Z shows the course of temperature before and after tuberculin injection in a Bactrian Camel (_Camelus bactrianus_) ♀ which lived for some months and showed no infection at autopsy.

Charts AA and BB show the temperature ranges of respectively a healthy and a tuberculous Bison (_Bison bison_.)

Chart CC is that of a Malayan Sambur Deer (_Cervus equinus_) which died a week after injection, showing fibrocaseous tuberculosis. The failure to make an initial rise is noteworthy, but the fall in temperature may be explained by the severity of the lesions and the approaching death.

Chart DD represents daily and post-injection records of a Virginia Deer (_Cervus virginianus_) which at death was found free of the disease. Chart EE is that of a healthy American Elk (_Cervus canadensis_).

[Illustration:

CHART Y. Composite chart of three non-tuberculous coatis. ]

[Illustration:

CHART Z. BACTRIAN CAMEL (Camelus bactrianus). Non-tuberculous. ]

[Illustration:

CHART AA. AMERICAN BISON (Bison bison). Non-tuberculous. ]

[Illustration:

CHART BB. AMERICAN BISON (Bison bison). Tuberculous. ]

[Illustration:

CHART CC. SAMBUR DEER (Cervus equinus). Tuberculous. ]

[Illustration:

CHART DD. VIRGINIA DEER (Mazama virginiana). Non-tuberculous. ]

[Illustration:

CHART EE. AMERICAN ELK (Cervus canadensis). Non-tuberculous. ]

SECTION XVII—