Part 24

Undulated Grass Parrakeet ♂ (_Melopsittacus undulatus_). Section of liver shows organic capsule normal. Nothing remains of the original structure by which it might be recognized, suggestion in places of granular cells resembling liver cells being only occasional occurrences and in small numbers. Where liver cells do occur they are highly granular in various degrees of atrophy and show various grades of nuclear retrogression. Greatest part of section consists of dense, white fibrous tissue in which lymphocytes are rather diffusely placed together with large numbers of epithelium-lined spaces. These spaces are often elongated after manner of imperfect ducts but are of irregular form, have single layer of low cuboidal epithelium and richly staining nuclei. Upon search certain acini are found to have especially hyperchromatic nuclei and penetration of basement membrane. In such localities collections of epithelial cells are to be seen in plug form in lymphatics and acini of imperfect development of lumen are found. In addition to these epithelial lesions connective tissue ones are seen, occurring generally in restricted localities. The interstitial framework is seen to consist of closely placed spindle cells, some of which are especially elongated after manner of imperfect ducts but are of irregular form, directed in a definite, purposeful manner, but interlace in the whorling manner noted in fibromas. Nuclei are, however, entirely too chromatic for a connective tissue tumor. Whenever a vessel occurs in these regions its lining endothelium is always swollen and nuclei in its wall will be proliferated and of embryonic type. This latter condition is apt to occur in patchy manner, part of wall appearing normal and other parts containing these peripherated elongated nuclei.

Secondary tumors were observed in the liver seven times as follows: Red Kangaroo (_Macropus rufus_) from malignant papilloma of the stomach; Spotted tailed Dasyure (_Dasyurus maculatus_) from cancer in the small intestine; Dorcas Goat (_Capra hircus_) from sarcoma in lymph nodes in mediastinum; Raccoon-like Dog (_Canis procyonoides_) from mixed tumor of thyroid; Undulated Grass Parrakeet (_Melopsittacus undulatus_) from a brain tumor probably glioma; another of same species from a sarcoma of pectoral muscle; European Robin (_Erithacus rubeculus_) adenoma of adrenal (_hypernephroma_).

SECTION VII THE ALIMENTARY TRACT, 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 ────────────┴────────────┴────────────┴──────┴─────┴─────────────