Part 22

It is almost certain that in a human pathological service of fifty-five hundred autopsies, one or more diverticula of the Meckel variety would be encountered and perhaps several of other kinds. In our material only pouchings or false diverticula of the colonic wall are recorded, and our personnel has often spoken of the absence of these gross abnormalities of the alimentary tract. The two cases, notes of which are given, are instances of hernial pouchings of the colonic mucosa and serosa, a condition which is well known in human medicine. It may be said to occur in two varieties, one in which the pouchings have heavy walls formed by a thickened mucosa, muscularis and peritoneum and one in which the bulgings have delicate walls, then being small herniæ of the inner coats through rifts in the outer. Such a division is probably unnecessary or misleading since the latter may be only a forerunner of the former. However the clinical evidence of the simple variety is scanty and may be little more than constipation while the peritonitic variety gives a clinical picture of pain, constipation and a mass in the left abdominal area, then known as diverticulitis or pericolitis sinistra. In these cases the colon is much distorted by the irregularity of its mucosa and by inflammatory thickening of the muscularis and serosa. Diverticula arise from defects of the muscular coat, or secondarily after inflammation or prolonged constipation, by weakness of muscle, or as hernial protrusions around the entrance of blood vessels where the muscle is thin. Such sacculations permit feces to collect and continue the inflammation, thus further weakening the gut and producing constipation, the whole vicious cycle being favorable to the formation of more sacculations; coproliths may form in the diverticula. The two monkeys now reported seem to have varying grades of the same condition, a long standing colitis with diverticula, constipation and the collection of inspissated feces in the sacculations. These animals did not have hemorrhoids.

Black Ape ♀ (_Cynopithecus niger_). Coprostasis. Coproliths in diverticulum. Chronic colitis. Cor bifida. The large intestine is of the same calibre as the small intestine should be when not distended. The sacculations as seen before opening the organ are salient, forming distinct pouches. In one or two cases they are so pronounced as to constitute diverticula 7 cm. long. In two instances the serosa at the fundi of these diverticula is markedly hyperemic and very thin. In many cases the sacculations contain coproliths. The wall of the organ is distinctly thickened, puckered, inelastic and opaque. Mucosa is thrown up into coarse rugæ.

Japanese Macaque ♂ (_Macacus fuscatus_). Chronic hypertrophic colitis. False diverticula of colon. The large intestine contains a moderate quantity of quite constipated feces. The serosa is smooth. The wall shows at several stretches enlargements of the normal sacculations, forming false diverticula. The wall of the gut in these herniæ is thinner than in the surrounding parts; no ulcers exist; no local peritonitis is present. The mucosa everywhere is irregular in thickness, less translucent than normal and thrown into irregular rugæ; tenacious mucus covers it. No ulcers.

TUMORS.

Only one tumor was observed in the mammalian intestinal tract proper. Dasyure (_Dasyurus maculatus_) Adenocarcinoma of the intestines. On postmortem there was a pale diffuse thickening of the coats of the small gut over a large area; numerous soft, light yellow, sharply circumscribed, elevated (like secondary tumors) nodules in the liver and spleen, and a pea-size whitish nodule around a bronchus in the right lung. Histological section of primary growth not made but a cross section of the intestine in the vicinity shows an adenomatous change with considerable increase in the connective tissue. The nodules in the liver, spleen and lung and the appearances of the abdominal lymph nodes, found microscopically, are precisely similar. They consist of irregularly arranged epithelial nests and distorted acini, around which are sharply outlined spaces, filled with the remains of degenerated blood or a granular material. The metastases are always sharply outlined.

Aves supply three papillomata which are interesting in that one occurred in the proventricle, and two grew in the duodenum in the vicinity of the upper biliary opening and presented within the lumen soft masses which, while not occluding the passage, offered some little obstruction as indicated by a slight distention above their location. In two, carefully studied, no indications of parasites or of cancer could be found. The birds concerned were an amazon, an owl, and a rhea.

SECTION VII THE ALIMENTARY TRACT, PART 2. THE LIVER

A consideration of the liver is anatomically and physiologically the next step in the discussion of diseases of the alimentary tract. While this organ may participate in most of the pathological states of the tubal part of the system, it is comparatively seldom the primary seat of change and when damaged seems to be possessed of great accommodative and reconstructive power. This must be true, and fortunately so, since we ascribe to it the major detoxicating function of the body. Nevertheless it is noteworthy that the largest solid organ of the animal body shows a relatively low percentage of changes threatening to life. In the sense of Pearl’s method of statistics, it does not “break down” easily. In pathology it is the custom to list with great care all the changes, gross and minute, in the liver, but with a few exceptions they are secondary or incidental. They do however reflect many things, especially referable to diet and to chronic infection from the intestinal drainage area. It is in these directions that the organ will be studied in the following pages.

Anatomically the liver is situated in the right upper part of the abdomen subjacent to the diaphragm in both mammals and birds, being held in position by attachment to this transverse partition, by ligaments or folds of peritoneum, and by the other abdominal viscera. Its general relationships do not offer great variations since in all animals means are afforded for a dual blood supply and an outlet for the hepatic secretion, the bile, into the higher intestines. Naturally variations in the size of the lobes are observed and there has been considerable speculation as to their independence and association. From the standpoint of comparative pathology, little can be ascertained to assist in this matter unless the position of abscesses and hepatitis relative to cholecystitis have a bearing; some discussion of this will appear later. We have not observed any peculiar pathology of the lobes of Spigelius and Riedel. In so far as the size and arrangement of the organ is concerned a few general facts of significance may be mentioned.

It was formerly thought that the liver varied inversely as the size of the animal but Magnan[23] and others have shown that the matter is not so simple. In the first place if there be an actual mathematical formula it is that the liver varies in size inversely as the surface area of the body, but this is not the whole story. It seems that the relation of size of the organ to its weight is not constant and that it is better to judge of the organic capacity by the latter. In herbivorous animals, both birds and mammals, the liver is lightest per kilo of body weight; next in weight are in order, fisheaters, meateaters, insectivora, seedeaters, fruiteaters and omnivora. There is besides this a roughly inverse ratio between the size of the liver and the length of the intestine and in the class Aves inversely as the size of the lungs also. From the immediately foregoing statements it is apparent that a bewildering variation occurs and that only rough measurements of the relative volume of the liver are available. An attempt was made in the Marsupialia, which present all the variations given, to discover if any peculiar pathology corresponded with the above groups; as it was fruitless, no change from our zoological treatment will be made.

Lobar arrangement varies from the relatively simple double avian type to the manifold lobulations of the seal or the marsupial but I can find no literature to indicate that lobes or lobulations have a direct effect upon functions. There must be a difference of blood supply for in certain infectious diseases like enterohepatitis and amœbiasis, the cystic and extreme right lobes are more affected than the left parts of the organ. In the bird this is not so difficult to follow since the three divisions of the portal vein, while they combine at times in an ampulla within the hilum of the liver, seem directed to certain lobes, that from the left portal seeming to point toward the right side. The avian portal system differs from the mammalian in having a large branch from the renal area, the so-called renal-portal system, pass to the liver, and by having a free anastomosis between the portal area and the caudal vena cava whereby blood from the pelvic district may pass into the general circulation without going through the liver. There is no unanimity of opinion as to the function or importance of this connection[24] and from the data collected here there is no peculiar renohepatic pathology.

The gall-bladder is not a constant organ in either mammals or birds and indeed it may be absent or present in very closely related species (Two- toed Sloth present, Three-toed Sloth absent). When present in mammals it is usually a dependent bag while in birds it commonly lies upon the cystohepatic duct, between the liver and the last curve of the duodenum, in some varieties filling from the bottom, the inlet being guarded by a valve. This cystic duct in nearly all birds, comes exclusively from the right lobe while the hepatic duct, with which the cystic has no connection, is formed by combination within the liver of radicles from both sides. It passes to the duodenum well in advance of the cystic duct, in some birds, _e.g._, the Struthiones, very near the pylorus, that is on the descending limb of the duodenal loop. By this means obstruction to the biliary stream is rendered difficult. The common duct combines with one of the pancreatic outlets in most mammals but the abdominal salivary gland in lower animals has more often patent separate ducts or multiple ducts than it does in man. Birds have one to four pancreatic ducts separate from the biliary openings.

The gall-bladder is missing in most varieties of the following groups: pigeons, parrots, wrens, ostriches, rheas, cuckoos, toucans among the birds; most odd-toed ungulates, hyraces, Indian elephants, all deer, peccaries, three-toed sloth, and many rodents. The varieties lacking this reservoir are herbivorous in the main, true carnivores seeming always to be possessed of such a structure. Among the important herbivorous ungulates, Bovidæ, Tragulidæ, Camelidæ and Suidæ have this bile reservoir almost without exception. Because of the interest now being shown in the pathology of the gall-bladder and its passages and of the pancreas, it was hoped that evidence of definite practical value for human pathology would be at hand in our study if we divided the animals into groups with and without a bile reservoir. The result is not unequivocal but worthy of note; it is discussed on pages 238 and 255.

Microscopically the well known lobular arrangement of the liver is rather faithfully carried out among the mammals albeit the most systematic and complete architecture is to be found in the pig while the marsupial seems the most disorderly, thus resembling the avian organ. In the latter class all the parts are indistinct, the cells having an unclear outline, the tubules being intricately wound and the interlobular connective tissue being scanty and not anastomosing in a definite framework. The intralobular reticulum is especially difficult to detect. Groups of cells are often found at portal spaces; these are large and small mononuclears and granular cells, probably of the hematopoietic system. It is possible that blood formation is performed in the liver and spleen in some adult birds but such a function is denied for the mammal except under very unusual conditions of bone marrow atrophy.

Glycogenic and fatty conservation is a function possessed by both zoological classes as are the detoxicating and bile-producing powers. However it is highly probable that urea and creatin in metabolism is not cared for by the avian liver as it is by the mammalian, judging by the researches of Paton and of Richet.

FAT DEPOSITS.

The care of fat by the liver is very well shown by examining the incidence of fatty metamorphoses through the various orders. In the first place Mammalia show a slightly higher percentage of fatty change than do Aves and should show a greater difference were it not for the large number of cases in two orders of the latter. Among mammals, lemurs, rodents and marsupials store fat in the liver more than other orders but in the second and third, it is chiefly the carnivorous varieties that have this property. Just why the slothful herbivorous lemurs should be first on the list is not evident especially since the grain-eating Ungulata are least apt to present fatty livers. With this exception, mammals with plentifully available hydrocarbons in their diet are most apt to show its deposit in the organ under discussion. Among the birds the gallinaceous varieties stand far ahead of all others, the passerines following next. Galli show the condition in association with acute infections, chronic diseases and in health. Unless there be distinct reason for it at autopsy, it may almost always be said to be normal. Passeres, especially the smaller forms, frequently come to autopsy with such excessively large livers, and indeed with a very large pad of abdominal fat, and nothing else, that one is compelled to look upon this overburdened organ as incapacitated by the deposit. These two orders increase the percentage value for the birds. Striges, Anseres, and Accipitres also show a good number of cases but there is among the Aves no such clear relationship between food fat and fat infiltration as may be found in the Mammalia.

AMYLOID DEPOSITS.

Amyloid deposit is reported with reasonable frequency in domesticated animals, causing in them a fairly definite entity, being as usual related to the effects of long continued or repeated infectious disease. Wild animals suffer from this condition but rarely and therefore to our few cases will be given a short discussion separately. An Indian Paradoxure (_Paradoxurus niger_) had patches of amyloid irregularly distributed through the organ. The animal had a carcinoma of the head of the pancreas, an obstructive biliary cirrhosis in a state of atrophy and a chronic nephritis with arteriosclerosis. There was nothing peculiar about the distribution of the deposit as there was in the next case, a Badger (_Meles meles_) where amyloid was found around the interlobular vessels and extending in the lobules along their canaliculi. This latter case seemed without cause and we have considered it a primary amyloidosis, the spleen, heart muscle, kidneys, intestines and other structures being affected. (See Fig. 7.) A third mammalian case concerned a Dasyure (_Dasyurus viverrinus_) which showed distinct intralobular collections. Its cause was a chronic suppurative process in the jaw bone.

Avian livers are somewhat more prone to show amyloid deposits, eight cases being on record. Four occurred in the Passeres, one each in Columbæ and Impennes and two in Anseres. Three were associated with chronic infectious disease and two with well established nematode parasitism. The remaining three, classed as primary, were not related to any other lesions, in two the amyloid liver being the only finding.

The next abnormal deposition related to the physiology of the organ is blood pigmentation. Normally hemic pigment is dispensed with very rapidly but under unnatural conditions it accumulates. In only one order is there any noteworthy percentage of hemosiderosis, the carnivores, the remainder showing a very trifling incidence.

DEGENERATIONS.

Going further into the physicochemical alterations of the liver brings us to consideration of those changes known as degenerations— parenchymatous, fatty, hydropic, hyaline, all of which we shall group under one heading. They occur in a great variety of conditions and do not appear to be specific, nor as the records are analyzed do they appear to occur preëminently in any one disease of the lower animals. The percentages are however higher for orders and families whose diet contains relatively more protein, carnivores, the higher marsupials, accipitrine, and wading birds.

ACUTE ATROPHY.

A very important degenerative disease of the liver is acute yellow atrophy or, better expressed, acute degenerative atrophy for it is a total destruction of the whole or large parts of the parenchyma. It is apparently toxic in origin being related to the toxemias of pregnancy, to certain organic and inorganic soluble poisons; some cases arise without discoverable cause. We have seen no cases in the mammal but two in birds. Both were females, one in active ovulation, while the other had no related pathology and the condition of the ovaries could not be determined since they had been destroyed after death by rats. The macroscopic and minute anatomy offers nothing new. Jaundice was present but not intense.

HEPATITIS.

True inflammatory lesions are to be defined as some form of parenchymatous change to which are added congestion, infiltration of round or polynuclear cells, stagnation in the bile ducts or perhaps actual degeneration of their lining cells. It seems necessary to stipulate these things because in the chronic forms, usually called cirrhosis, it is necessary to have all of them, plus efforts at regeneration, in order to determine it as a chronic progressive process. Acute hepatitis is a rare condition in mammals except when it is combined with septicemia or severe enteritis. In birds on the other hand the liver is, aside from the intestinal wall, perhaps the most frequent seat of pathology in the abdomen. This is because of its almost constant involvement in infective enteritis, and in such conditions as fowl cholera, fowl typhoid, coccidiosis and cecal amœbiasis, all of which we have sporadically. When one searches for special distribution among the orders, only one of them stands out as having a high percentage, the Galli, an order which seems to have a very vulnerable liver.

The macroscopic anatomy of hepatitis in birds is peculiar in showing a definite swelling with spots of gray or yellow color, sometimes coalescing to form irregular areas. These are much more definite than in the mammalian organ where swelling and hemorrhage are the commoner findings. These pale spots are of two origins. They may be focal necroses of the hepatic cells, with or without circumferential congestion or hemorrhage to make them stand out. In amœbic, coccidial and typhoid livers such is the type of change. In septicemia and cholera, the mottlings are made up of increased interstitial mononuclear areas, with blood cells and shadow cells numerously present. I have seen what was in all probability a stage of repair after both these kinds of change. In the former, regeneration seemed to take place from adjoining liver cells, there being in the section no evidence of increased bile ducts to make new hepatic cells. It seemed also that phagocytes were derived from blood cells and not from Kupffer’s cells. In the infiltrative lesion disappearance of the liver cells from the groups leaving compressed and deeply granular remnants was all that could be determined. Regeneration seemed to be progressing in the manner just outlined.

NECROSES.

The degenerative and infiltrative areas of acute hepatitis are simulated by focal necroses in livers not the seat of a general hepatitis from which they can be differentiated only by the microscope. These small areas of local tissue death are quite common in all pathological processes but are most common in the liver, possibly because of its exposure to toxins from the intestine. Their exact origin is not determined, various explanations being given. The somewhat distinct distribution in mammals _versus_ that in birds may help in the final decision. In the former, focal necroses are more often encountered midway in the anatomic lobule and around the central vein whereas a perivascular location seems the usual position in the bird.

Massive necroses of the liver may be of considerable importance in veterinary medicine. They take their origin in several different ways. The commonest in our records are those due to cecal coccidiosis and amœbiasis (quail disease and blackhead) while from the primary seat of these two infectious diseases, the cecum, may originate the virus of nonspecific hepatic necroses. We have observed several birds, passerine, psittacine and gallinaceous, which at autopsy showed a distention of the cloaca, ceca, and lower small intestine with urates and slime but no mural inflammation and a large area of necrosis in the liver. This suggests perhaps a “white diarrhœa” but it did not occur in epizoötics and other morbid anatomy of this specific disease was absent. These frequent instances of association between the colonic area and the liver seem to suggest the transfer of necrotizing organisms, just as amœbæ travel, and to indicate measures to clean out the tract when birds become “plastered.” Massive necroses also arise from mould disease, and from infection with the necrosis bacillus, emanating from nearby infectious foci, or _via_ the normal passageways from the intestine. Massive areas of degeneration may form by the coalescing of numerous foci, in any septicemic disease.

ABSCESS.

In man, amœbæ, flukes, cestodes and biliary tract infection are the commonest causes of purulent collections within the liver. In the lower mammals parasites play practically a solitary rôle at least as the major influence in localizing the collection, bacteria from the intestine doing the rest. We have one case of massive abscess in a porcupine suffering with septic pneumonia, the suppuration in the liver being due to the colon bacillus, the general septicemia probably being from distemper. Monkeys have shown more abscesses than any other order, three being observed. One was due to infestation with trichocephalus which had apparently penetrated from the colonic wall into the liver through adhesions formed between these two structures. Another seems certainly amœbic but these protozoa could not be found, while the third followed an ulcerative enterocolitis of unknown cause. Two cats were seen with parasitic abscesses; one harbored _Distoma_ or _Clonorchis sinensis_, the other a nematode of ascaris type.

The topographic distribution of these six hepatic abscesses was interesting. The position of the abscess is not mentioned in one case but of the remaining five three were entirely in the right lobe, one had the major lesion on the right side and smaller separate abscesses spread over the organ, and one with about equal distribution in all lobes. All three confined to the right side were solitary.

Abscesses of considerable size are not met with in the bird as in the mammal perhaps because the former does not form real pus, necroses developing instead.