Part 20

TABLE 12. _Showing the Percentage Incidence of Various Forms of Inflammation in the Alimentary Tract of Ungulata._ ══════════════════════════════════╤═════════════════╤═════════════════ Lesion │ Group A │ Group B │ Perissodactyla │ Ruminants and │ and Swine, Wart │ Relatives Per │ Hogs, Peccaries │ cent. │ Per cent. │ ──────────────────────────────────┼─────────────────┼───────────────── Acute fermentative gastritis │ 18.│ 2.1 All other forms of gastritis │ 16.3│ 5. Acute toxic or fermentative │ 1.6│ 2.3 enteritis │ │ All other forms of acute enteritis│ 1.6│ 8.4 Chronic enteritis │ 0.│ 1.9 Colitis and typhlitis │ 0.│ 3.1 ──────────────────────────────────┴─────────────────┴─────────────────

Ungulates as a class stand in a position equivalent to the Primates in the incidence of gastrointestinal diseases. They show a conspicuous percentage of cases apparently due to incorrect food and, coupled with this, a high percentage of gastric involvement, being exceeded in this respect by the marsupials only (there is an adequate reason for this—see below). Cases ascribed to bacterial or parasitic agents are not numerous. Analysis of the records of the two groups discussed above brings out some interesting facts. Consultation of Table 12 shows percentage comparisons, based on the number of autopsies, of lesions in the various sections of the tract. Group A, that with the simple stomach and the short capacious colon, is represented by forty-four specimens, while Group B embraces 321 animals. Perhaps the use of these two widely differing figures for comparison is open to some objection which might be final and decisive were not the figures so definite. At a glance one can see that Group A has involvement more marked high in the tract while Group B has more disease in the intestine and colon. Certainly gastritis is more common (five times) in the A than in the B group, while enteritis is more common in B (over three times). No case of chronic enteritis or of involvement of the colon is recorded in animals with a simple stomach and a wide hind-gut. This may be read either in terms of vulnerability of the stomach or in the degree of resistance of the respective groups.

Consideration of the local factors of the stomach brings to light at once the fact that incorrect food entering the simple stomach could attack the softer, less resistant glandular section of the fundal and pyloric areas whereas the rumen and psalter of the compound organ, with their stratified epithelium devoid of glands, act as barriers or as places where detoxication of irritants might take place. In both groups bulky food is packed to the left, the esophageal and cardiac section in the simple form, the rumen in the compound. Soft or liquid food may pass into the psalter and abomasum of the ruminant stomach almost directly since it has not the force or bulk to push aside the valve-like fold of wall at the junction of esophagus, rumen and reticulum. For this reason, if for no other, the character of soft food supplied to this order must be unexceptionable.

It has not been possible to follow out the layering of diets as Scheunert did when showing the course of various foods before they are mixed at the beginning of the pyloric compartments. We have seen two cases in ruminants which seem to indicate that soft food had passed into the right side cavities of the stomach, there to cause irritation, while the rumen remained quite normal. It seems, however, accepted by veterinarians that excessive soft food may be followed by trouble in the digestive stomachs, while excessive dry food may cause distention of the left hand sections. So far as I know, the relative incidence of gastric disorders in the above outlined groups has not been pointed out before.

The pathological types of gastroenteritis do not present many unusual features. Simple injection of vessels during digestion seems more evident in this than any other order, while mucus production seems less marked. The mucosa of the reservoir portions may, in simple overfilling and fermentative distention (gastric tympanites), be quite normal or dull red; when active fermentation has occurred it may be digested and peel off. More or less true inflammation as seen in the digestive stomachs is definitely better expressed in the compound ruminant organ than in the simple equine variety where congestion and edematous swelling with hemorrhage form the usual picture. True catarrhal changes both gross and minute, are often well seen and ulcerative lesions are not uncommon; ulcers are unusual in the simple stomach. These statements hold good also for the small intestine. Enteritis affects the duodenum and jejunum more in the Perissodactyla and swine than in the ruminants. Ungulata do not react with hyperplasia of the mural lymphatics as do many other orders, but the swelling of the mesenteric nodes is often noteworthy. As might be expected this is more definite with catarrhal changes and therefore best seen in the ruminants. In the colon, however, the solitary follicles are often quite prominent in simple inflammation. Histologically the greatest changes seen in this order are superficial degenerations with mononuclear increase in the deep submucosa, mostly arranged in perivascular fashion. The villi do not contain the large number of cells seen in the Carnivora.

MARSUPIALIA.

Consultation of the figures for this order in Table 11 arrests attention at once because of the peculiar percentages found under the detailed factors. Thus food is of no moment as a disturber of the alimentary tract, while bacteria and parasites are high in importance. The gastric segment is more often attacked than any other portion and slightly more often than in the nearest order, Carnivora. These unusual figures deserve explanation, to which purpose it will be necessary to consider the anatomy of the organ and to discuss why bacteria and parasites stand so high in etiology.

Marsupials are divided into six families in our classification (see page 44) which in regard to their diet, range from largely carnivorous (the first two) through those choosing mixed insects, fruits and vegetables (the second two) to those eating vegetables and grain (the last two). The stomach of these animals does not vary exactly according to their diet, the first four, opossums, dasyures, bandicoots and wombats, possessing an organ closely similar in outline and construction and resembling the carnivorous variety, while the phalangers and kangaroos have a stomach entirely different from the first four although somewhat similar to one another. The first group has a round or irregularly elliptical organ with the esophagus and pylorus close together along the lesser curvature. The wombats have a bank of glands surrounded by a capsule, near the cardia. The stomach of the first four animals is divided into cardiac, fundal and pyloric parts by the construction of their mucosa, the first mentioned division being a high, rounded pouch, rumen-like, well to the left. The phalanger’s stomach is more elongated, the two openings well separated and a fissure is found in the right end of the lesser curvature which serves to separate the pyloric part from the rest. The Macropodidæ all have a stomach resembling the human colon in being elongated, with longitudinal bands gathering it into sacculations. There is a distinct esophageal section to the left with a blind sac suggesting an ungulate rumen, a long tubular fundal, and a sacculate pyloric division.

The small intestine of the order starts with the opossums as a stout muscular and mucous tube fitted for meat eating, but as one proceeds to study the families downward in the list this tube becomes more delicate and longer. In the first two families the cecum is rudimentary and the colon very short as in cats, but the length and capacity of these parts increase through the bandicoots and wombats until in the strict fruit, vegetable and grain eaters, phalangers and kangaroos, the cecum is long and capacious and the colon relatively long and roomy.

TABLE 13. _Showing the Incidence of Gastroenteric Disease in the Two Forms of Marsupial Intestinal Tracts._ ═══════════════════════╤═══════════════════════╤═══════════════════════ │ Group A │ Group B │Carnivorous Stomach and│Herbivorous Stomach and │ Intestines 103 │Intestines 73 Specimens │ Specimens Per cent. │ Per cent. ───────────────────────┼───────────────────────┼─────────────────────── Acute gastritis │ 9.6 │ 15. │ Bacteria Verminous │ Bacteria Verminous Chronic gastritis │ 0. 13.6 │ 5.4 0. Acute enteritis │ 2.9 │ 1.5 Colitis incl. typhlitis│ 1.9 │ 4.3 ───────────────────────┴───────────────────────┴───────────────────────

Table 13 contains an analysis of the forms of gastroenteritis as they were described in the two groups of tracts, that resembling the carnivorous, that similar to the herbivorous intestinal construction, and according to the factor believed to be responsible. In the first group gastritis of an acute nature occurred in 9.6 per cent. of the 103 specimens. They were chiefly catarrhal in character and seem for the most part secondary to verminous infestation; at least six of the ten cases were associated with parasites. The process microscopically is catarrhal and deeply infiltrative. Group B has a high incidence of gastritis and here the evidence of bacteria or toxins is quite plain. Several of the cases were in animals showing also Kangaroo disease of the jaw with pneumonia or septicemia; the gastric lesion of streptothricosis will be described under that heading. The character of gastritis without jaw disease is somewhat different from that with it. Pathologically the process is a congestive and superficially necrotizing affair, forming upon the tips of the folds, small gray erosions or flat shallow irregular ulcers, which upon histological study consist of loss of tissue of the mucosa and some deep congestion with round cell groups but no reaction deep in mucosa or submucosa. True catarrhal inflammation has occurred, but not like in the opossums.

Chronic gastritis in the simple stomachs is almost exclusively in opossums harboring _Physaloptera turgida_, a worm which fastens itself more or less firmly in the mucosa and probably, with the assistance of bacteria, causes sufficient irritation to produce a hypertrophic change in the deeper layers and a destruction of the glands where it holds and a distortion of those nearby. One is reminded that Fibiger found spiroptera to be responsible for adenocarcinoma in rats; no tumor formation has been found in these animals, although one opossum with such a stomach had an adenocarcinoma mammæ. Small hemorrhagic spots may occur in the deeper layers, possibly where the worms have bitten. The rugæ are irregular or interrupted by knobs and papillæ.

Group B, stomachs showing chronic change, were all kangaroos. The three cases resembled the infiltrating necrotizing lesions as discussed under ulcers (page 175). The process showed an infiltration of the subsurface tissues with a gray slough over the densest part. The mucosa as a whole was irregularly rugous and spotted with red gray areas.

Altogether one gets the impression that in the simpler stomach, reactive inflammation is most prominent, while in the colonoid stomach degeneration is greater than reaction.

Intestinal lesions in marsupials are not common and not peculiar except in that they carry out the pathological reaction as seen in the stomach. The carnivorous intestine shows frank catarrhal changes, the herbivorous presents congestions and superficial necroses. These two groups then follow the descriptions as already given for carnivores and ruminants.

The colon presented in the first group, simple catarrhal or follicular change. In the second division the lesions resembled those in the stomach; they were only once of the three instances associated with streptothricosis.

AVES.

The class Aves has been treated in the chart precisely as have the mammals, but it is not possible to make the accurate diagnoses or to separate groups of lesions according to anatomy as was done for the latter class. Upon the average there is more gastroenteritis among birds than mammals, but when looking for an explanation of this, it was unfortunately necessary to enter in the “undecided” column of Table 11 a very great number of cases. This column would be greater relatively were it not for the parasites in parrots and gallinaceous birds, the entries for which are high. Besides this fact and that the owl stands at the top, the pigeons at the bottom of the list numerically, no further general statements are allowable. There are several orders with high values among those of which insufficient autopsies are at hand to cast percentages.

The avian alimentary tract seems to have developed according to the character of food the different varieties of birds consume if one may judge by the construction of the bill, the gastric musculature and the intestinal wall. Zoological classification has only secondarily considered this point, it being made incidental to the habits and habitats of birds. For this reason the orders as outlined on pages 44–46, placed as they are in historical evolutionary position, represent with few exceptions groups which have differing diets and, by the same token, differing gastrointestinal tracts. Classifications based upon habits of life (Raptores, Cantores, Natores), prove likewise too broad or too heterogeneous, while systems making character of food the chief criterion though apparently correct in reasoning and helpful in certain orders, (Accipitres, Galli) are found to present copious exceptions; moreover we are imperfectly informed of the exact diet that many families require or resort to in absence of their preferred food. I shall therefore discuss the chief diseases and distributions according to our classification, preceding the discussion by a brief résumé of the anatomical peculiarities of the avian alimentary tube.

The first digestive burden falls upon the proventricle where the principal juices are secreted while the muscular stomach or gizzard assumes the duty of gastric mastication. The lateral muscular bellies of its heavy wall grind the food and mix well the gastric juices. Its mucosa probably supplies only lubricant. In birds whose food is hard, corn and the like, this grinder is supplied with a dry horny internal layer, while a thick, moist, soft, epithelial surface is sufficient for carnivorous birds. All kinds of gradations exist between these extremes. The mucosa of the proventricle is always soft, but quite deep to permit the placement of compound tubular glands.

The relation of size of these two parts is subject to many variations.[22] The proventricle is larger proportionately in meat eating, fish-eating and fruit eating birds, the gizzard having the greater size in granivora and insectivora. In certain birds the mucosa of the two is separated by a very soft thin zone, an important fact in Psittaci since at this place spiroptera seem to penetrate to the glandular layer of both organs.

The duodenum begins in practically all birds, from a spherical cavity at the pyloric end of the gizzard, to be accredited anatomically to both sections. It passes downward, forms a long loop enclosing the pancreas, its distal end lying under the liver and near the gall-bladder. Near its end it receives the major bile and pancreatic ducts; smaller ducts from the liver and pancreas may enter near the pylorus or elsewhere along the loop. The small intestine is usually simple in its coils, but in the birds that eat grain, grass and greens, may be long and complicated. So too the colon, usually a very short segment, may be increased in the just mentioned group while the ceca are only of any considerable length in herbivorous birds. The length of the ceca is, according to Owen, related to the availability of food and the need the bird may have for exhausting the nutritive value of it. In carnivorous birds as in similar mammals, the whole gut, but especially the hind-gut, is very short and the ceca small or absent. But so they are in picarian birds which are chiefly herbivorous, but may eat meat.

GASTRITIS.

The double-muscle stomach, that with the two lateral plates and tough epidermal internal coating, is seldom the seat of disease. An excess of greens in the diet sometimes seems to soften or macerate the lining, while an excess of pebbles may cause erosions. Upon severe irritation this internal layer assumes the appearance of tanned leather and may crack. The proventricle of such a gizzard seems rather resistant to disease, particularly one would say, to infective processes, for catarrhal or ulcerative inflammation is uncommon. The saccular stomach with uniform muscular walls continuous with those of the proventricle, such as is seen in raptatory birds and parrots, offers a somewhat different picture. The internal membranes of these organs are definitely softer, seeming to swell with great ease, and the glands themselves are smaller both at the fundus and outlet, a construction which may favor their closure by swelling from simple congestion and edema. Catarrhal and ulcerative processes are definitely more common in such organs than in the first type or true gizzard.

ENTERITIS.

Enteritis of all orders is most outspoken in the duodenal loop, but a determination of the lesion must be made with some care. All the signs of intestinal inflammation—congestion, swelling and opacity, excess mucus or mucopurulent covering—must be present to justify a gross diagnosis of enteritis and even when these exist one fails at times to confirm the finding by microscopical section. These changes may be simulated by digestive activity so that it is but reasonable to demand them all in a clear cut fashion before applying the term enteritis. However, it is well known that cases in both human and veterinary medicine giving a satisfactory clinical picture of this disease may fail to show to the naked eye and under magnification the changes expected.

In the human being, the carnivore and the ruminant, the ileum presents the most definite picture of enteritis. In the bird, the duodenum shows the prominent lesions, and with the exception of specific diseases like blackhead, is always involved when the smaller coil of small intestine is affected. This is true whether the enteritis be nonspecific or be associated with cholera of chickens, ducks or parrots.

The colon presents peculiar lesions in but few birds. Ulcerative and necrotizing processes have been encountered in three orders, Psittaci, Anseres and Herodiones, suggestively like the specific forms seen in the ceca. Microscopy and one unsuccessful culture failed to reveal a mould or protozoön. The condition appears as a gray white plaque in the cloacal wall or it may spread up to the colon and around the urethral orifices. At times it is superficial upon the mucosa and may be covered by a pseudomembrane.

The chief interest in the ceca centres about enterohepatitis either of heterakis and amœbic origin or that supposed to be due to coccidia or Bac. scoticus. This specific form has been encountered only in Galli (three of the four families). It has been so well described by Hadley, Smith, Morse and Cushman that it is unnecessary to discuss it since we have nothing to add to its pathogenesis or pathology. At a later time some attention will be given to our experience with Quail disease. What is more interesting from a comparative standpoint, besides having a bearing upon blackhead, is the discovery of heterakis in the ceca, and hemorrhage and fatty change in the liver without amœbæ or coccidia in either place (unfortunately no bacteriology was done), in a Sebastopol Goose (_Anser domesticus_), a bird which has ceca not unlike the gallinaceous varieties. This is a single observation and must be treated expectantly.

Microscopically the avian digestive tract in its various inflammatory states presents a few noteworthy features. The primary reaction, sometimes the only one, to irritation is injection of the vessels in the villi or deeper mucosa. To this, however, is nearly always added a granularity of the epithelium, without much evident mucus (goblet cell) formation. When the epithelial degeneration is marked there appears a round cell increase in the deep mucosa shortly followed by a similar infiltration into the villi. True catarrhal enteritis as described for the cats is not as common as some combination of the changes just detailed, but when it occurs is best developed in the carnivorous avian tract. The most striking cellular finding is the round cell of the infiltrate. It is of the middle lymphoid size with clear protoplasm, or, when late in the disease, may be small and so-called adult. Polynuclears, unless eosinophilic, and endothelioid cells are rare.

The foregoing are general remarks concerning the pathology of the avian tract, and we are now ready to discuss briefly the reactions of the orders. I shall, however, omit mention of those in the right half of Table 11.

Passerine birds are represented better than any other order because they are more numerous in nature and therefore exhibited more generously in collections. This order is not especially vulnerable as to its alimentary tract, but this tube is often affected by tiny stones, bits of rust from cages and by acute general nonspecific infections to which these birds are quite susceptible. Upon many occasions intense congestion with and without tiny hemorrhages in the duodenum are all that can be found in the little birds and the diagnosis of enteritis is put down. Only about one-tenth of these birds have shown more or less definite catarrhal changes. Many birds have heavy infestation with worms which may activate bacteria.

The Striges and the Accipitres will be discussed together because of the similarity of their tracts and their diets. The reaction of their gastric complex has already been mentioned and what was written there can be extended to the intestine. The type of lesion is catarrhal and seems to be “meat bred” although this cannot be proven. They never have given positive heart’s blood cultures so that the disease seemed not to be septicemic. Liver and spleen have harbored colon and paracolon bacilli. It will be noticed that they have the highest incidence of gastric disease.