PART 3

. THE PANCREAS

The pancreas, an organ functionating as a gland with an internal secretion and by pouring a digestive juice into the duodenum, remains a structure of constant anatomy throughout the zoological classes under discussion in that it is composed of compound racemose lobules whose outlets join to form large discharging ducts, and of interstitial bodies, the islands of Langerhans, without connection with the secreting acini but having some relation with the blood and lymph vessels. The organ originates embryologically by sprouts from the side of the primitive gut just below the part destined to be stomach, and from an outbudding of the common biliary duct. These two sprouts or pouches combine to form one organ, but this does not necessarily effect a union between their lumina. In some birds and mammals (Accipitres and some Ungulata) the lobes of the pancreas remain distinct during life, and the discharging tubules seem to empty only their respective lobes. However, there is no uniformity in the matter, and indeed the anatomy of the ducts is subject to very great variation despite the rather similar beginnings of the organ. Those who are interested in this point may consult Beddard,[25] Letulle and Nathan-Larrier,[26] and Opie[27]; there will be given in the following pages the average findings of anatomy of the gland body and of its ducts.

The region of the pancreas in lower animals, especially those which travel constantly on four feet, is one of great activity, and the organs are more freely movable than in the human being. The only exception to the latter part of this statement may possibly be found in the cats and dogs, in which there are firmer attachments of the duodenum and pancreas to the vertebral column and the liver; this is brought about by the short gastrohepatic omentum and the abrupt curvature of the duodenum toward the back, under the mesenteric stalk. In the Ungulata and Marsupialia and in some Rodentia, the pyloric, duodenal, and pancreatic attachments are relatively loose, and torsion of the pylorus seems to be allowed for, since in these animals great distention of the stomach is the rule. Among the Aves the anatomy is wholly different. The birds have no attachment of the duodenum and pancreas to the posterior abdominal wall, except indirectly through a narrow strip comparable to the gastrohepatic omentum, one division of which passes to the beginning of the duodenum, the other to its end, and by a thin tail of pancreas which goes toward the spleen. The bulk of the pancreas lies in the U made by the long free duodenal loop, the two organs being covered by the serous membranes forming the middle abdominal sac. It will be seen from the foregoing that the movability of the pancreas is considerable—a highly necessary provision, because the stomach and duodenum are also movable and subject to distention by food and alteration of position during flight.

In the class Mammalia there are usually two ducts, one entering the duodenum in combination with the bile duct, the other variously above or below this common opening. As will be seen in Table 14, however, there are several exceptions to this statement, there being but one duct opening independently of the bile duct. The general anatomy is closely similar throughout this class, so I shall confine my notes to the exceptions from the general rule, especially where they seem to be of importance in the etiology of pancreatic lesions.

In the class Aves the pancreas consists usually of two or three distinct lobes lying one in front and two behind the cleft between the limbs of the duodenal loop, and it discharges its secretion into the duodenum by two or three ducts separately, and almost invariably above the bile duct openings. One duct always opens near the top of the distal end of the duodenal loop, near the bile duct. In the gallinaceous birds that have a bile duct opening into the duodenum near the pylorus, there is usually a pancreatic duct opening there also. In some birds a third duct passes from the body of the pancreas to the duodenum at different places along the loop. It does not seem probable that dislocation of the duodenal loop would seriously interfere with the passage of the pancreatic secretions, since the gland is so intimately related with the duodenal serosa, but obstruction to the biliary flow due to changes in position of the intestine is easier because the bile duct is separate and loose and arises from the end of the gall-bladder. The ducts of both these structures pass very obliquely through the duodenal wall a matter of importance, as will be seen when discussing the infiltrative forms of enteritis. The gall-bladder is not present in all birds, but this is probably of no importance, as the hepatic ducts are wide and run directly from the liver to the duodenum. The pancreatic ducts are short and are closely bound around by glandular tissue up to a place quite close to their entrance into the intestine.

The musculature of the gall-bladder and the ducts seems comparable in mammals and birds, and a constrictor or sphincter usually called the muscle of Oddi, is present in all but pigeons (Oddi). There may be found also muscular fibres in the major ducts of the pancreas, but they are not so heavy nor distributed so definitely as similar tissue in the bile duct walls. The mucosa of the pancreatic duct is much more folded in birds than in mammals, seemingly, therefore, more adapted to obstruction by swelling from any cause.

Passerine birds have two pancreatic ducts usually on the ascending loop of the duodenum, or there may be one ahead of the pyloric biliary duct. The picarian varieties possess three ducts as a rule, one near the beginning of the pylorus, one near its end and a third of inconstant location. Owls have a system like Passeres, but the relation between the organ and the intestinal loop is looser and the ducts are wider. Columbæ have two pancreatic ducts in the ascending limb of the duodenum. Gallinaceous varieties have a double biliopancreatic system, a duct of each kind entering the descending and the ascending duodenal reaches, with the biliary placed after the pancreatic in each instance. Accipitres have always two and oftentimes three ducts as do Anseres, both orders frequently having the third duct opening at the bottom of the duodenal loop where stagnation can and does occur. Fulicariæ have usually three ducts.

The foregoing are the orders presenting pancreatitis and therefore those whose anatomy concerns this study directly. The irregularity in number and arrangement of ducts continues through all the avian orders which show a greater aberration from standards than do the mammals. Theoretically the birds should cast some light upon the unsettled question of the causes of pancreatitis, and as a matter of fact such a result seems to have been realized. In 1915 I published an article upon a study of this subject which indicated that acute inflammations of this organ may arise _via_ the lumen of the duodenum and pancreatic ducts, while chronic processes were the result of periductal passage of pathogenic agents. Further study would seem to indicate that disease of the biliary tract is of importance in lesions of the pancreas since a decidedly large number of cases is found in mammals, where the relation of ducts is definitely more intimate than in birds. The work of Archibald,[28] Deaver and Sweet,[29] and Judd[30] seem to agree with the findings upon our material. This need not be, however, in discord with the idea that acute inflammation is superficial in origin, chronic lesions deep or lymphogenic. The discussion will be resumed in a subsequent paragraph.

The amount of pancreas to be found in birds is greater than that in mammals. According to our figures the organ represents ¹⁄₄₀₀th of the body weight in the former and ¹⁄₆₀₀th in the latter. These figures are averages of a small number of instances and are not final. It is, however, obvious to casual daily observation that birds as a class have a large pancreas.

The minute structure of the organ is governed by the same general rules throughout the two classes under consideration. Birds do not have as many interstitial islands as do mammals, but they are more compact and seem more definitely constructed of coiled tubules. In so far as the internal structure of the organ is concerned there has not developed in our study pathology peculiar to any animal. The importance of the ducts and position of the organ will be discussed later.

Recognition of pancreatic disease during life is practically impossible. In human medicine the signs and symptoms are vague and inconstant,[31] diagnosis often being a matter of exclusion. Veterinarians, except under the best hospital conditions make no attempt to diagnose pancreatic lesions but, since the improvement of surgical practice, at times operate upon cases of evident pain and distention which prove to be pancreatitis. These things were evident in a deer that I saw and that died on the following day from acute hemorrhagic pancreatitis; I made no attempt at this diagnosis, believing it to be acute tympanites. The feces were normal, according to the judgment of persons qualified to give an opinion.

The condition of the pancreas at autopsy on animals not dying with lesions of this organ deserves some attention since it may confuse the uninitiated. If the organ be seen in its normal resting stage shortly after death, it is not difficult to recognize the condition as normal for the species. Activity is indicated by a darker or redder color and an increase of consistency. In carnivorous or omnivorous animals and birds the pancreas in this state is a body with a distinct bulky character, whereas in strictly herbivorous varieties, especially ungulates, the structure is diffusely pink and doughy. This is important since the early stages of self-digestion and decomposition assume this same character in all varieties, while later stages present a deep red, swollen, wet organ. These appearances must be differentiated from acute hemorrhages or inflammations, a distinction based upon actual local blood collections or extravasations and areas of degeneration in true disease. Oftentimes differentiation must be made under the microscope and in advanced decomposition, determination is impossible. When there is torsion of the stomach, notably in ungulates, the pancreas is often found decidedly congested. This, it seems, is due to a twist of the duodenum and passive congestion of it and the pancreas—the only simple explanation despite the apparent provision for a high degree of mobility, as already explained. The organ is nearly always mildly congested in severe grades of acute duodenitis, although it need not be pathologically involved. It is, however, noteworthy that the pancreas is an organ with a low morbidity index, especially when one considers its proximity to a structure showing the highest disease index in the body, the intestine. The succeeding paragraphs will reveal in comparison to other organs only a small number of cases of degeneration, inflammation and tumors. This has been ascribed to the freedom of blood supply and the power of tryptic digestion.

An expression of this relative immunity to pathologic change is met in analyzing the data upon the simplest lesions, degenerations, to be expected in many states of disease. Only a small number of cases present themselves, and they are under expected conditions, namely in association with acute general infection, sometimes definitely septicemic in nature. About half of them were discovered microscopically, affecting the islands of Langerhans in vacuolization or granular disintegration. Focal necroses of the organ were met four times, three turkeys and a cockatoo. It is noteworthy that all these birds had some involvement of the liver, twice a complete acute hepatitis and twice a cholangitis. This is the more interesting since we shall learn that the liver is less often involved in avian than in mammalian pancreatitis. Hemorrhages occur occasionally in the pancreas in acute general infections and are seen in acute inflammations of the intestines; the percentage incidence with the latter is, however, very small. Pancreatic apoplexy proper has not occurred, for all the instances of large hemorrhage into the organ have been combined with changes forcing a classification of acute pancreatitis.

PANCREATITIS.

Pancreatitis in the acute form is divided by many writers into exudative, hemorrhagic and necrotizing, while for the chronic variety an inter- and intra-acinus form has been described. It is questionable whether it is fair in acute cases to focus attention by special nomenclature on different macroscopic pictures, unless it be for descriptive purposes solely, since there is nothing at hand to indicate that differing agents cause one kind every time. The physical findings seem to depend rather upon the speed of operation of the causation than upon its essence. Sudden obstruction of the pancreatic duct is believed to produce necrotizing processes to which hemorrhage may be added by digesting of blood vessels. Exudative cases seem due to extension of ulcerative inflammation, from a perforated gastric ulcer for example, to which digestive pancreatitis may be added. The interacinus chronic inflammations are usually considered as due to obstruction or infection through the biliary or pancreatic ducts whereas vascular disease produces intra-acinus connective tissue overgrowth. Analysis of the records of this laboratory would seem to indicate that necrotizing and hemorrhagic processes belong together, exudative in a class by themselves, and that chronic disease may be either interlobular or intra-acinar without regard to associated pathology. I have therefore studied our cases from this standpoint.

Pancreatitis has occurred in thirty-eight mammals and birds among the 5365 autopsies, an incidence of 0.7 per cent.; class incidence in mammals twenty-seven or 1.5 per cent.; birds eleven or .3 per cent. (Table 14.) Among the higher class all the important orders are represented, but by no means in equal degree, whereas in the birds, less than half of the orders are listed, with the important Psittaci missing, despite a high death rate.

It is perhaps well to be guarded in stating the relative vulnerability of the pancreas in various orders, but one cannot avoid the observation that Carnivora stand well in advance of the others (3. per cent. of autopsies), to be followed by Ungulata (1.9 per cent.) and Rodentia (1.7 per cent.). Nor can one fail to see that mammals have inflammations of this organ five times as often as do birds.

TABLE 14. _Showing Cases of Pancreatitis, their Pathological Nature, the Character of Ducts of the Particular Animal, the Associated Pathology, All of Which Data are Collected at the Bottom into Totals for Zoological Classes and Orders._

════════════╤════════════╤════════════╤══════╤═════╤═════════════ Order │ Acute │ Chronic │Number│Open │Cholecystitis │Hemorrhagic │Pancreatitis│ of │with │ │ or │ │Ducts │Bile │ │Necrotizing │ │ │Ducts│ │Pancreatitis│ │ │ │ ────────────┼────────────┼────────────┼──────┼─────┼───────────── Primates: │ │ │ │ │ Marmoset │ │Chr. Dif. │ 2 │ 1 │ 0 │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ Carnivora: │ │ │ │ │ Wolf │Ac. Hem. │ │ 1 │ 1 │ ? Fox │Ac. Hem. │ │ 1? │ 1 │ 0 Bear │ │Chr. │ 1 │ 1 │ 0 │ │ │ │ │ │ │ │ │ │ Raccoon │ │Chr. sl. │ 1? │ 1 │ 0 Bear │Ac. Nec. │ │ 1 │ 1 │ 0 Coati │Ac. Hem. │ │ 2 │ 1 │ 0 Badger │Hem. and │Chr. │ 2? │ 1 │ ? Ocelot │Ac. Hem. │ │ 2 │ 1 │ +? Bear │Ac. Hem. │ │ 1 │ 1 │ 0 Wild Cat │ │Chr. │ 2? │ 1 │ 0 Lion │Ac. Hem. │ │ 2? │ 1 │ 0 Skunk │Ac. Nec. │ │ 2? │ 1 │ ? Raccoon │Ac. Nec. │ │ 1? │ 1 │ 0 │ │ │ │ │ Rodentia: │ │ │ │ │ Beaver │Ac. Hem. │ │ │ 1 │ 0 Porcupine │Ac. Hem. │ │ │ 1 │ 0 Ungulata: │ │ │ │ │ Antelope │Ac. Hem. │ │ 1 │ 0 │ 0 Deer │Ac. Hem. │ │ 1 │ 0 │ Deer │Hem. │ │ 1 │ 0 │ Deer │Hem. │ │ 1 │ 0 │ Elk │Ac. Nec. │ │ 1 │ 0 │ Nylghaie │Ac. Hem. │ │ 1 │ 0 │ 0 Peccary │Ac. Hem. │ │ 2 │ 1 │ 0 Marsupialia:│ │ │ │ │ Phalanger │Ac. Nec. │ │ 1 │ 1 │ 0 Opossum │Ac. Nec. │ │ 1 │ 0 │ 0 Opossum │Ac. Nec. │ │ 1 │ 1 │ 0 Devil │ │Chr. │ 2? │ 1 │ + Passeres: │ │ │ │ │ Finch │ │Chr. │ 3 │ 0 │ 0 Thrush │Nec. and │ │ 3 │ 0 │ 0 │Hem. │ │ │ │ Chaffinch │ │Chr. │ 3 │ 0 │ 0 Picariæ: │ │ │ │ │ Hornbill │Acute │ │ 3 │ 0 │ 0 Striges: │ │ │ │ │ Owl │ │Chr. │ 3? │ 0 │ 0 Accipitres: │ │ │ │ │ Kestrel │ │Chr. │ 3? │ 0? │ 0 Columbæ: │ │ │ │ │ Dove │ │Chr. │ 2 │ 0 │ 0 Galli: │ │ │ │ │ Pheasant │ │Chr. │ 2 │ 0 │ 0 Fulicariæ: │ │ │ │ │ Gallinule │Ac. Hem. │ │ 3? │ 0 │ 0 Anseres: │ │ │ │ │ Gadwall │Ac. Hem. │ │ 3? │ 0? │ 0 Struthines: │ │ │ │ │ Ostrich │Ac. Hem. │ │ 3? │ 0? │ 0 ════════════╪════════════╪════════════╪══════╪═════╪═════════════ _Totals_ │ │ │ │ │ Primates │ 0 │ 1 │ │ │ Carnivora │ 10 │ 4 │ │ │ 4? Rodentia │ 2 │ │ │ │ 1 Ungulata │ 7 │ │ │ │ Marsupialia │ 3 │ 1 │ │ │ 1 ────────────┼────────────┼────────────┼──────┼─────┼───────────── _Mammalia_ │ 22 or 1.1% │ 6 or .32% │ │ │ 6 Passeres │ 1 │ 2 │ │ │ Picariæ │ 1 │ │ │ │ Striges │ │ 1 │ │ │ Accipitres │ │ 1 │ │ │ Columbæ │ │ 1 │ │ │ Galli │ │ 1 │ │ │ Fulicariæ │ 1 │ │ │ │ Anseres │ 1 │ │ │ │ Struthiones │ 1 │ │ │ │ ────────────┼────────────┼────────────┼──────┼─────┼───────────── _Aves_ │ 5 or .14% │ 6 or .17% │ │ │ Grand Total │ 27 or .5% │ 12 or .22% │ │ │ 6 ────────────┴────────────┴────────────┴──────┴─────┴─────────────

════════════╤═════════════╤═════════╤═════════════╤═════════╤═════════ Order │ Cholangitis │ Hepatic │Inflammation │ Acute │ Chronic │ or │Cirrhosis│ outside │Enteritis│Enteritis │Choledochitis│ │ Pancreas │ │ │ │ │ │ │ │ │ │ │ │ ────────────┼─────────────┼─────────┼─────────────┼─────────┼───────── Primates: │ │ │ │ │ Marmoset │ 0 │ 0 │Lymphadenitis│ 0 │ 0 │ │ │ adjacent │ │ │ │ │ glands │ │ │ │ │ │ │ Carnivora: │ │ │ │ │ Wolf │ + │ 0 │ 0 │ + │ 0 Fox │ 0 │ 0 │ 0 │ ? │ 0 Bear │ 0 │ 0 │ Areolar │ + │ │ │ │ tissue and │ │ │ │ │ glands │ │ Raccoon │ 0 │ 0 │ 0 │ 0 │ 0 Bear │ 0 │ 0 │ Slight │ + │ 0 Coati │ + │ 0 │ 0 │ 0 │ 0 Badger │ + │ Atr. │ 0 │ 0 │ Ocelot │ +? │ 0 │ 0 │ + │ 0 Bear │ +? │ 0 │ 0 │ + │ 0 Wild Cat │ 0 │ 0 │ 0 │ + │ +? Lion │ 0 │ 0 │ 0 │ + │ + Skunk │ + │Infective│+ Lymphnodes │ 0 │ 0 Raccoon │ 0 │ 0 │ 0 │ 0 │ 0 │ │ │ │ │ Rodentia: │ │ │ │ │ Beaver │ + │ 0 │ 0 │ 0 │ + Porcupine │ 0 │ 0 │ Lymphnodes │ + │ 0 Ungulata: │ │ │ │ │ Antelope │ 0 │ 0 │ 0 │ 0 │ 0 Deer │ ? │ 0 │ + │ + │ 0 Deer │ 0 │ 0 │ + │ 0 │ 0 Deer │ 0 │ + │ 0? │ 0 │ 0 Elk │ 0 │ 0 │ Lymphnodes │ + │ 0 Nylghaie │ 0 │ 0 │ 0 │ + │ 0 Peccary │ 0 │ 0 │ 0 │ + │ 0 Marsupialia:│ │ │ │ │ Phalanger │ 0 │ 0 │ 0 │ + │ 0 Opossum │ 0 │ 0 │ 0 │ + │ + Opossum │ 0 │ 0 │ 0 │ + │ 0 Devil │ + │ 0 │ + │ 0 │ + Passeres: │ │ │ │ │ Finch │ 0 │ 0 │ 0 │ ? │ ? Thrush │ 0 │ + │ 0 │ 0 │ 0 │ │ │ │ │ Chaffinch │ + │ 0 │ 0 │ 0 │ 0 Picariæ: │ │ │ │ │ Hornbill │ + │ 0 │ + │ + │ Striges: │ │ │ │ │ Owl │ +? │ 0 │ 0 │ 0 │ + Accipitres: │ │ │ │ │ Kestrel │ 0 │ 0 │ + │ 0 │ + Columbæ: │ │ │ │ │ Dove │ 0 │ 0 │ 0 │ 0 │ + Galli: │ │ │ │ │ Pheasant │ + │ 0 │ 0 │ 0 │ + Fulicariæ: │ │ │ │ │ Gallinule │ + │ 0 │ 0 │ + │ 0 Anseres: │ │ │ │ │ Gadwall │ 0 │ 0 │ 0 │ + │ 0 Struthines: │ │ │ │ │ Ostrich │ 0 │ 0 │ 0 │ + │ 0 ════════════╪═════════════╪═════════╪═════════════╪═════════╪═════════ _Totals_ │ │ │ │ │ Primates │ │ │ 1 │ │ Carnivora │ 4 │ 2 │ 3 │ 7 │ 2 Rodentia │ │ │ │ 1 │ 2 Ungulata │ 1 │ 1 │ 3 │ 5 │ Marsupialia │ 1 │ │ 1 │ 3 │ 2 ────────────┼─────────────┼─────────┼─────────────┼─────────┼───────── _Mammalia_ │ 6 │ 3 │ 8 │ 16 │ 6 Passeres │ 1 │ 1 │ │ │ Picariæ │ 1 │ │ 1 │ 1 │ Striges │ 1? │ │ │ │ 1 Accipitres │ │ │ 1 │ │ 1 Columbæ │ │ │ │ │ 1 Galli │ 1 │ │ │ │ 1 Fulicariæ │ 1 │ │ │ 1 │ Anseres │ │ │ │ 1 │ Struthiones │ │ │ │ 1 │ ────────────┼─────────────┼─────────┼─────────────┼─────────┼───────── _Aves_ │ 4 │ 1 │ 2 │ 4 │ 4 Grand Total │ 10 │ 4 │ 10 │ 20 │ 10 ────────────┴─────────────┴─────────┴─────────────┴─────────┴─────────

════════════╤════════ Order │ Fat │Necrosis │ │ │ ────────────┼──────── Primates: │ Marmoset │ 0 │ │ │ Carnivora: │ Wolf │ 0 Fox │ 0 Bear │ + │ │ Raccoon │ 0 Bear │ 0 Coati │ + Badger │ 0 Ocelot │ + Bear │ 0 Wild Cat │ 0 Lion │ + Skunk │ 0 Raccoon │ small │ Rodentia: │ Beaver │ 0 0 Porcupine │ 0 Ungulata: │ Antelope │ ? Deer │ 0? Deer │ 0 Deer │ 0 Elk │ 0 Nylghaie │ 0 Peccary │ + Marsupialia:│ Phalanger │ + Opossum │ + Opossum │ + Devil │ + Passeres: │ Finch │ 0 Thrush │ 0 │ Chaffinch │ 0 Picariæ: │ Hornbill │ Striges: │ Owl │ + Accipitres: │ Kestrel │ 0 Columbæ: │ Dove │ 0 Galli: │ Pheasant │ 0 Fulicariæ: │ Gallinule │ 0 Anseres: │ Gadwall │ 0 Struthines: │ Ostrich │ 0 ════════════╪════════ _Totals_ │ Primates │ Carnivora │ 5 Rodentia │ Ungulata │ 2 Marsupialia │ 4 ────────────┼──────── _Mammalia_ │ 11 Passeres │ Picariæ │ Striges │ 1 Accipitres │ Columbæ │ Galli │ Fulicariæ │ Anseres │ Struthiones │ ────────────┼──────── _Aves_ │ 1 Grand Total │ 12 ────────────┴────────

Further analysis of the data leads into a consideration of the anatomy of the viscus in terms of the acceptable theories of the origin of the lesion. It is commonly believed that infection of the gland occurs by passage of organisms through the duct opening in the intestines, especially when there is swelling of the mucosa of both. For the human being the idea is current that infection or obstruction of the common bile duct may spread to the pancreatic duct, and that mechanical or inflammatory obstruction of the papilla of Vater may permit the bile to pass up the pancreatic duct. This theory is based upon certain observations, notably those of Opie, in cases, where a gall stone obstructed the ampulla, bile entered the pancreas and acute pancreatitis arose, partly by the activating action of the bile upon the pancreatic juice and partly by bacteria introduced at the same time. This method of origin is perhaps accepted in most quarters, but there are some who believe that infection of the gland may occur by the infiltration of lymphatics around the pancreas by disease of adjacent parts—gall- bladder, stomach or lymph nodes. Quotation has already been given to reference literature, and I shall not go further into theory except in pointing out how our material may help to answer the question.

In the first place it seems perfectly obvious that infection might in any animal travel from the intestine to the pancreas _via_ its ducts, the main question to be settled being the relative importance of the infection _via_ the bile duct. Let us now see if the variations in anatomy will cast any light upon the matter.

Among the 1860 mammals, there are as far as I can determine 1275 which have one pancreatic duct opening in conjunction with the bile duct, 585 in which the former has an intestinal opening independent of the latter. Among this 1275 there are nineteen cases of pancreatitis, while among the 585 there are eight cases, or as 14.9 to 13.6. All Aves have separate biliary and pancreatic ducts and relatively little pancreatitis, although frequently suffering with its most common accompaniment, namely duodenitis. There is therefore some evidence that more pancreatitis occurs when there is a physical proximity or combination of bile and pancreatic ducts.

Active infections of the biliary system in relation to pancreatitis are, however, not as conspicuous as might be expected. In the mammals twelve of the twenty-seven cases showed cholecystitis or cholangitis; in every instance the form of pancreatitis was acute. Among the eleven avian cases four showed inflammation of the biliary channels, but not of the bladder. Hepatic cirrhosis was observed four times. In a thrush and a skunk obvious infectious cirrhosis existed, and in both a necrotizing pancreatitis was found. A badger suffered with atrophic cirrhosis of the liver and a chronic pancreatitis with acute exacerbation. A deer showed marked perilobular fibrosis with a recent hemorrhagic pancreatitis probably due to duodenal torsion. Nothing very distinctive is to be found in these cases, but they merely make the total of involvements of the liver and its adnexa up to twenty. It is to be emphasized that pancreatitis was not associated with lithiasis in ducts or bladder as described on page 240. Peripheral cholecystitis and plastic inflammations about the pylorus and lesser omentum are exceedingly rare in wild animals, while they are not common in human surgical practice. They did not occur at all in mammals in this series, the only external inflammations being in lymph nodes in cases of frank infectious character. There were distinct adhesions between liver, duodenum and pancreas in two birds, one with acute, the other with chronic pancreatitis.

In so far as the kind of pancreatitis is concerned mammals had twenty- two acute and six chronic forms, one animal having the former implanted on the latter, while birds had five acute and six chronic. The preponderance of acute over chronic lesions in mammals again recalls the association of the biliary and pancreatic ducts, but if one expect that such a relation establishes acute inflammation, the relatively high figures for Rodentia and Ungulata, with a single duct removed from the bile duct conflict with the data for orders having two ducts such as the Carnivora. Every case in the former orders was of acute nature; only two had any hepatic disease, four had lymph gland hyperplasia in the pancreatic region, and seven had acute enteritis. The preponderance of acute over the chronic cases in mammals and the nearly equal number in birds is, however, apparent.

The collateral pathology with the most definite relationship to pancreatitis is enteritis and one may say that the former occurs in proportion to the incidence of the latter. Acute forms, twenty-seven, were associated with acute enteritis nineteen times. Chronic enteritis was found with chronic pancreatitis in six of eleven cases.

There is a rough relationship between the type of pancreas and the nature of the lesions. The organ may be divided for this purpose into the compact organ firmly held in place by attachments to the lesser omentum, spleen and duodenum, and the velamentous organ which spreads a considerable distance along the duodenum and sends out digitations into the mesentery and thin processes toward the spleen. The first type is seen in primates and carnivores and birds, while the second is characteristic of rodents, ungulates and marsupials. The compact variety showed all but one of the chronic cases while the loose organ was affected by the acute pancreatitis in twelve of thirteen cases.

The microanatomy of the cases may throw a little light upon our subject. I was able to see the duct in one case of acute pancreatitis (bear). It showed a simple catarrhal inflammation with a very moderate circumferential round cell increase. The destruction of glandular areas by edema, hemorrhage and necrosis offers nothing of importance except in a few birds. In these the necrosis is more definite about cross sections of ducts, and the islands of Langerhans are frequently spared until necrosis is locally complete. In a case of chronic pancreatitis in a bird, a cross section of pancreatic duct was found in the intestinal wall; a chronic catarrhal and infiltrative enteritis existed in this specimen. A very definite mantle of round cells was found about the duct while the mucosa showed no change, although the lumen seemed large. Interlobular fibrosis was the rule, only one case of intra-acinar pancreatitis being encountered; this specimen, a bird, showed great distortion of the acini and of the islets.

The study of comparative pathology of pancreatitis does not settle its etiology, but some very suggestive facts may be learned. The association of hepatic and biliary disease and of enteritis in the causation of pancreatitis seems amply confirmed, and the latter factor is in our series numerically the greater. It is suggestively shown that inflammations of the pancreas occur more frequently in the zoological class in which the ducts of the organ and of the liver empty into the duodenum together or in close association. Moreover, infections of the liver and adnexa are very important in the mammals, more so than birds in which enteritis, notably chronic in type, usually accompanied the involvement of the pancreas. This is consistent with the incidence of bile tract disease as already discussed under that subject, and it is interesting to note that the mammals showing the greatest number of cases of choledochitis and cholangitis also show the high case incidence of pancreatitis. The birds that have bile tract disease have little pancreatic disease. These facts when considered in connection with the free biliary supply of the avian duodenum, the disassociation of the ducts of the two glands and the close apposition of the pancreas to the duodenal wall, suggest strongly that direct infection of the pancreas can occur from the intestinal wall along the walls of the ducts perhaps via the lymphatics. This is supported by the observation of at least one case in which there was a definite inflammation under the adventitia of the pancreatic duct, its mucosa being normal. The study also suggests that acute pancreatitis is more often associated with acute lesions in the intestines and with hepatic or gall-bladder disease, and that chronic pancreatitis seems more often the result of chronic or repeated intestinal inflammation. Peripheral inflammation such as occurs in gastric or duodenal ulcers, has not been encountered in a distinct character so that its value cannot be estimated.

[Illustration:

FIG. 20.—ADENOMA OF PANCREATIC DUCTS. CORSAC FOX (CANIS CORSAC). ]

Cystic change in the pancreas has been observed a few times, but never a large visceral collection or the so-called extra-pancreatic cysts of the omentum. One acinus cyst was seen in a drake, one congenital cyst in a lark, and multiple ductal cysts were seen in a baboon and a duck. The parenchyma in all cases seemed entirely capable of functionating.

TUMORS.

Tumors of the pancreas have been three in number, two being of academic interest only. One of these concerned an apparent adenoma of the ducts within the organ, discovered microscopically in the sections from a Corsac Fox (_Canis corsac_). This is the only specimen we have had, and I can find no description of the normal microanatomy of this species, so that with a knowledge that certain carnivores have convoluted ducts, the determination is made tentatively; it corresponds microscopically to a ductal adenoma. The pancreas of a raccoon (_Procyon lotor_) showed a true adenoma of glandular acini as two separate but closely applied firm nodules surrounded by a capsule, and with distorted acini as seen under magnification. The most important tumor was found in an Indian Paradoxure (_Paradoxurus niger_), an adenocarcinoma involving the head of the organ, enlarging it to twice its normal size; there were no metastases. The animal suffered also with an infective hepatic cirrhosis of recent origin, chronic nephritis of the arteriosclerotic type, chronic fibroid splenitis. No obstruction to the biliary channels existed.

SECTION VII THE ALIMENTARY TRACT,