Chapter IX: Section VII: The Alimentary Tract. Part 1.—pharynx, Esophagus, Stomach and Intestines (1)

The portion of the anatomy that we now approach varies in construction almost as much through the animal kingdom as do the external shape and covering of the various orders and much more than do the other systems. The reason for this is obvious, an arrangement accommodative to the differing food chiefly, but not a little to the ease with which animals obtain and assimilate their nutriment. It would be impracticable to describe all the variations of the orders discussed in this study, but since certain gross and minute differences are of importance in comparative pathology they will be discussed at the appropriate places. It is my purpose to present in a subsequent section a discussion of food in captivity from the standpoint of its quality and quantity in relation to pathology.

Doubtless the quality of food is the largest factor in the production of disease both of the alimentary tract and elsewhere, but I am not at all sure that the quantity may not be equally important, in certain groups at least. Thus, for example, the ungulate has nearly always available in bedding a substance that he can and will eat, and the prevalent idea that an animal will eat only as much as is good for him seems not to hold at all times, since overfilled rumens are only too common. It might be thought, however, that captivity creates a sort of pica, or that enforced idleness is conducive to gorging. The use a few lines above of the word “doubtless” may have arrested the attention of some, yet when the whole subject is reviewed it seems entirely justified. Plimmer puts incorrect food at the head of the list of the causes of enteritis, Brooks emphasizes the importance of certain grasses and musty fodder, systematic writers detail among the principal causes of gastritis spoiled food, and in zoological gardens specific disease like hog cholera and enterohepatitis are relatively uncommon while nonspecific gastroenteritis is the most frequent diagnosis in causes of death.

The other factors to which enteritis is ascribed are animal and vegetable parasites and mechanically operative foreign bodies, the last being unimportant. Just how important the first mentioned are is a matter of some question which must be subjected to considerable study before any solution can be expected.

If for no other reason than that the gross and minute pathological anatomy of gastroenterocolitis is the same through the mammals and birds (aside from a few specific lesions like enterohepatitis, typhoid fever, etc.), while the food and bacteria vary, it would seem probable that the ultimate cause is the same, a poison which can be formed alike in the carnivorous and herbivorous gut, and not dependent upon bacteria, but upon the chemistry of the food or of the intestinal mucosa. To put the matter more simply, the lesions being the same under nearly all conditions is not the cause the same, and is it not a poisonous product from food or the intestinal lining. It is profitable here only to mention the marked similarity of enteric lesions under the differing conditions and in different orders. We shall study chartwise, the various forms of inflammation from the cardia to the anus in terms of their anatomical diagnosis and most probable etiology in an attempt to throw light upon the matter, and later present the physiology. System requires, however, some attention first to anatomical order so that a brief review of the esophageal and pharyngeal conditions is indicated.

PHARYNX.

The buccal-pharyngeal cavity in mammals is used chiefly as a passage way for food and as the place where some of them triturate and insalivate the bolus. Certain orders, Primates, rodents and marsupials, use this cavity thoroughly at the first mastication, others use it little at first but may ruminate, the ungulates, while strict carnivores use it very little. The Aves use their pharynx almost exclusively as a passage, and, despite the presence of a certain amount of salivary gland tissue, probably do not digest any substance in this cavity. The crop or ingluvies is a sac to permit of salivary digestion but is really a storehouse to allow rapid feeding without overfilling of the proventricle. The esophagus extends from the pharynx to the cardiac opening of the stomach in mammals and widens into the glandular stomach or proventricle in birds, the upper end of which lies in front of the lower third of the left lung behind the heart.

Inflammations of the buccal, pharyngeal and esophageal walls are relatively common in certain orders especially ground birds and grazing ungulates. This would seem to be explained on the basis of injury to the mucosa by sharp or pointed objects picked up while feeding. The character is usually necrotizing, but need not be, and the bacteriology is not specific. Definite infectious diseases like diphtheria and actinomycosis are not included here, but it might be mentioned that the second disease cited is believed to be started by the penetration of the organisms into wounds made by sharp grasses. Certain orders, notably Ungulata, Passeres, Psittaci and Struthiones, are quite susceptible to mycotic infestation and we have seen an outbreak of thrush in Kites (Accipitres). It is, however, interesting and possibly significant of peculiar protective powers in the upper alimentary tract, that strict carnivores have failed to show ulcerative, purulent or necrotizing inflammations of the mucosa from the mouth to the cardia. There has been no important data upon ingluveal indigestion or esophageal obstruction. Birds especially, and occasionally mammals, gorge themselves or take too large a bolus, but it seems as if this is only fatal where some distinct important pathology is present which has reduced their resistance. In the lower esophagus one has to deal with worms in connection with the proventricle in birds, but no mammals seem to have suffered with temporary or permanent strictures. “Crop-binding” has occurred in the following orders: Psittaci, Galli; and overfilling of the esophageal dilatation was seen in Accipitres and Herodiones; Columbidæ with their double crop were not affected by this abnormal collection of food in the esophagus.

DILATATIONS OF ESOPHAGUS.

The mammals have shown three dilatations of the esophagus interesting enough to detail briefly:

Mongoose Lemur (_Lemur mongoz_) ♂ . Sacculo-fusiform dilatation of
esophagus, probably congenital, with adjacent fibrosis of lung. In
poor condition for several years but recovered satisfactorily from a
bad cut inflicted by cage-mates. At autopsy the general condition is
poor, hair missing in spots, all skin dry and atrophic with patches of
keratotic dermatitis. All tissues anemic, muscles lusterless. Right
lung collapsed, brown and pink, spotted with anthracosis. Left lung
pushed forward and to left by a mass in the posterior mediastinum.
Lower lobe in its posterior portion is adherent to esophageal mass.
Lower half of this lobe beginning where bronchus ends and extending
over anterior-posterior surfaces shows marked fibrotic processes and
at one point in tissue between end of bronchus and adherent esophagus
there is no lung tissue remaining. No recent consolidations. Bronchial
lymph nodes, small, firm homogeneous pale brown with specks of
anthracosis. Heart contracted, normal in size, firm red-brown. Aorta
is firmly adherent to esophageal mass where bronchus crosses it. The
lower half of the esophageal from the hilum of the lung to the cardia
is the seat of a dilatation, fusiform for the most part, but with a
saccular portion anteriorly. This latter presses the left bronchus
upward and heart forward. The wall of the tube is slightly irregularly
thickened but there is no cicatrix and mucosa shows slight
hypertrophic condition. A large mass of food occupies the dilatation.
Stomach is empty save for gas. Mucosa is soft, smooth, pale pink.
Duodenum shows slight swelling of the rather pale yellow submucosa and
mucosa, but the tips of the villi are injected. Intestine contains
only a little slimy mucus. Large intestine contains a mass of
constipated feces. The esophageal dilatation seems to have been
congenital although it is barely possible that the fibrosing
pneumonitis and pleuritis may have aided and caused it by traction. It
has been doubtless the cause of the animal’s inanition.

Black Bear ♂ (_Ursus americanus_). Sacculate dilatation of esophagus
with chronic esophagitis. Chronic hypertrophic gastritis. Chronic
lymphadenitis. Fatty degeneration of liver. Acute catarrhal enteritis.
Had been vomiting more or less, nearly every day for two months and
did not eat for six days before death. Mouth, pharynx and esophagus
are full of macerated, unrecognizable food. Pharynx seems normal.
Larynx is yellow, mucosa rough and slightly thickened in places
especially just above the vocal chords. No excess of mucus. Esophagus
in neck is dilated. Mucosa is rough, irregular yellow brown. This
dilatation proceeds downward so that at thoracic opening tube is twice
normal size. Upon entering thorax this dilatation turns to right and
in irregular saccular form extends to diaphragm compressing heart and
lungs to left. The main course of it then recrosses the midline, aorta
being slightly twisted as it regains position in front of vertebræ.
The wall is irregularly thickened from pseudomembranous patches and
some hypertrophy of mucous and submucous layers. Muscle and serous
coats are considerably thinned. The sac is full of macerated food and
gas. The right lung is compressed small resilient red gray. No
adhesions in either pleura. On section the lung tissue is found to be
slightly edematous, red gray, compact and while not atelectatic yet
crepitates much less than normal. Left lung is the seat of passive
congestion in lower lobe and lower half of upper lobe. The upper half
of lobe is compressed and subcrepitant like the right lung. Lymph
glands of neck and thorax are much enlarged firm with large irregular,
clear outlined follicles and brown firm homogeneous pulp. The aorta
shows slight roughening, the intima being smooth and homogeneous.

Lion ♂ (_Felis leo_). Ten and one-half months old. Cystic
parenchymatous goitre, dilatation of esophagus, ulcerative enteritis.
Acute glomerular nephritis. Chronic hyperplasia of spleen. Fatty
infiltration of liver. Bronchopneumonia (from pressure of goitre).
Ascaris in intestines. Had lump on neck for several weeks, ate very
little and seemed to have hard work to get anything down. Stopped
eating toward the last and vomited water and foam. There is a small
ulcer with everted lips just below left incisor on lower lip which the
keeper says is of several months’ duration. The thyroid is much
enlarged and forms a large mass in the upper chest and extends far up
in the neck. Because of this mass the lungs are pushed far down in the
chest. Heart also lies very low. The thyroids are enormously enlarged
and cystic, the right measuring 13 × 8.5 × 5 cm. and the left
19 × 9 × 5 cm. The lungs are pale pinkish white. Air content increased
in places, decreased in others. No hypostatic congestion. The lungs
seem normal except at the apex where they are collapsed probably from
pressure on lung by enlarged thyroid which dips down into the chest
for at least three inches filling entirely the apex of the chest. One
bronchial lymph gland was about the size of a walnut, the rest were
normal. The heart seems normal except for its slightly low position.
The abdomen contains about 300 c.c. of deep yellow highly albuminous
fluid. No adhesions. The liver is softer than normal, glistening,
smooth, moist and very yellow particularly at the edges. The gall-
bladder contains a green mucoid bile and the duct is patulous. Spleen
and kidneys are normal. Mouth and pharynx are normal. The esophagus is
much dilated above the thyroid. The enlarged thyroid pressing upon it,
has acted as a distinct obstruction. In this pouch was a large amount
of food probably (from the history) eaten two days before. The
esophagus below this point was normal except for the presence of thin
mucus. Stomach empty save for two small bits of meat. The duodenal
walls are much thickened, mucosa covered with small ulcers many with a
hemorrhagic base; there were present also a few small, round worms.

FIG. 14.—DILATATION OF ESOPHAGUS. LION (FELIS LEO). DILATATION
PROBABLY DUE TO OBSTRUCTION BY ENLARGED THYROID BODY. IN
ILLUSTRATION DISTENTION OF ESOPHAGUS CAN BE SEEN IN THE FORK OF THE
THYROID LOBES.
]

Here are presented three different dilatations, the first probably congenitally started and aided by pulmonary fibrosis, therefore secondarily a traction diverticulum, the second probably entirely congenital, and the unusual third case due to obstruction by an enlarged thyroid. In this connection might be mentioned small saccular diverticula in the proventricle of a Fire Finch (_Lagonosticta senegala_), and at the pylorus in a Puma (_Felis concolor_). Neither of these seemed of any significance and played no part in the death of the animals; they did not seem to be artificially produced, by worms, for example.

THE PROVENTRICLE.

The proventricle or forestomach of birds, is the seat of active secretion of the gastric juice in nearly all orders, although Jobert believes that the mucosa of the gizzard may contribute some digestive fluid, and there are active glands in this tissue in a few orders. The proventricle does not act as a reservoir during digestion, but as soon as the juices are well mixed with the bolus the food is passed on to the gizzard. The organ has a rather free position, at least as far as its left lateral and downward movements are concerned for the left lateral abdominal air sac is free on that side of the gastric complex and the left lateral thoracic also extends down the side of the proventricle. Upward and anteriorly is the heart. Some of the cases of proventricular spiropteriasis have shown very marked congestion of the left lung, possibly due to the closure of the anteroinferior air sac aperture on that side. Aside from parasitism, affections of this organ are not very numerous.

Infestation with spiroptera and with less dangerous worms was quite serious at one time, but since routine examinations of all suspicious birds has been practiced this parasitism has been under control. This is a subject of especial importance to collections, and will be described in a special section. The susceptibility of the proventricle to damage seems from our figures to be very distinctly a matter of zoological order. In so far as parasites are concerned, the parrot group stands away ahead of all others having an incidence among autopsies upon Psittaci of 16 per cent.; after them come the Picariæ with 9 per cent., and Columbæ and Passeres each with 4 per cent. When, however, non- verminous conditions are reviewed the anserine birds are found the most susceptible, 3 per cent. of the autopsies upon this order revealing proventricular lesions; after them come the Columbæ, 2 per cent., and Psittaci, 1.5 per cent. In this group are included inflammations of all kinds, dilatations and distentions and some lesser matters.

This part of the stomach has been involved in our cases of fowl diphtheria, showing a distinct mucopurulent inflammation with penetration into the depths of the glands; no separation of the mucosa occurred, but ulceration was seen. Perforation was observed thrice, twice by ulceration around a worm while it was boring into the muscular layer and once, in an ostrich, by the penetration of a nail. Obstruction of this division of the stomach by impaction of food and stones is not common, but does occur. The reason for such obstruction is usually very obscure. Sometimes it seems due to the feeding of seeds and the like in too finely divided form, whereby food and pebbles are taken up together. Some of the smaller birds have had in times past too many small pebbles in the cages, while others have had too large seeds, thus apparently trying to use the pebbles to crush them. It would seem also that the birds had really eaten too much and could not accommodate it in the gullet and gizzard; this seems surely true in three or four Accipitres. Most often, however, we have had to fall back upon the inadequate explanation of pica or perverted appetite.

Impacted proventricles and gizzards have been observed thirty-four times, in eight of which it seemed the sole cause of death, and therefore probably entirely due to foreign bodies in food. The theory is accepted that dilatation and obstruction will not occur if the motor power of the gastric wall be normal and no inflammation exist. In this regard we can only discover five birds (the mammals will be discussed later) with any distinct inflammatory or degenerative disease of this part of the anatomy and two with lesions elsewhere which might affect the musculature; this leaves the vast majority of gastric obstruction in birds unexplained on basis of defective motor power, therefore probably dependent upon the character of material consumed. The anserine birds and parrots are most often affected by this form of obstruction.

Acute or chronic dilatation of the forestomach and gizzard is very rare in birds, it having occurred only thrice in our records, a finch, a parrot and an owl; the causes were entirely unknown since the cavities were not overfilled with food.

THE STOMACH.

Impaction of the mammalian stomach is a diagnosis made but once in our records, an Indian Antelope (_Antilope cervicapra_), and this is viewed with suspicion. The rumen was undoubtedly tightly packed, being distended to its fullest capacity with rather dry and not properly softened grain. However, postmortem changes had advanced and therefore observations in the whole body were not dependable. The bulk of food which can be accommodated by the rumen is very large, and had this not been dry and firm the condition might not have been interpreted so seriously. Many animals come to autopsy with a well filled, indeed even with a well packed stomach, but there is usually sufficient reason for this or there is distinct pathology to account for death.

All this of course implies a stomach of normal or approximately normal dimensions since distention beyond this, or dilatation of the stomach, is more definite. In veterinary medicine, gastric tympanites (rumen alone or all stomachs, or the simple stomach) is ascribed to food that ferments easily when taken in excess or in the presence of defective motor power, to constrictions by scars and to obstructive tumors; excessive feeding is sometimes mentioned but given a subordinate rôle. Our records throw very little light upon the subject since only five cases were observed. Four of these five seem to be due to acute fermentation independent of gross physical obstruction, while one, a Cape Hunting Dog (_Lycaon pictus_) showed an old chronic ulcerative gastritis with both healed and active ulcers distorting the pyloric end of the organ. Three of the first mentioned four were monkeys and one was an ocelot. The stomach of the voracious monkey is at time of dissection usually well filled, but in these cases there seems no doubt that gas and excess fluid had distended the cavity enormously, in one instance apparently assisting in acute cardiac dilatation. There were no obvious reasons for assuming any damage to the gastric motor mechanism.

FIG. 15.—ROUND ULCERS IN STOMACH WALL. COMMON OPOSSUM (DIDELPHYS
VIRGINIANUS). THERE IS GENERAL MODERATE CHRONIC GASTRITIS WITH ROUND
ULCERS NEAR THE CARDIA.
]

GASTRIC ULCERS.

Gastric ulcer, so-called peptic or round ulcer of the stomach, having a chronic course and leading to radiating scars of the mucosa is not common in the lower animals, but frequent enough in the human being. The form of ulcer in question has at present no adequate explanation, or at least there is no one cause which will answer for all cases. Local injuries from within or without the stomach, bacterial embolism, entrance of bile through the open pylorus and many other factors have been named in the causation but can seldom be used in any given case. In the lower animals with their relatively frequent parasitic infestation, another factor is added. In analysis of our statistics I have separated ulcerative gastritis from parasitic and mycotic ulcerations and from peptic ulcers; the first is discussed in later paragraphs. Parasitic ulcers of the stomach occur chiefly in our native marsupial, the opossum, and in some Carnivora; physaloptera, strongylus, ascaris, and gastrophilus have been found. The kangaroos are frequently affected (8 cases) with an acute or subacute ulceration of the gastric wall, without much general gastritis. The lesion is peculiar in appearance. The youngest ulcers are black or dark gray, flat necroses of the mucosa alone and indeed the process very frequently penetrates no deeper. Older lesions spread laterally and may be preceded by a very narrow congested line but there is no raised edge nor does there seem to be submucous infiltration. If the process be rapid a loose dirty slough may form. Certain of the advanced cases of Kangaroo mycosis will present more infiltrative lesions of the gastric wall leading to large and well defined necrotic areas; they may at times penetrate the whole wall outward. (See page 580.)

True peptic ulcers have been found in Primates, 4; Carnivora, 5; Pinnipedia, 2; Insectivora, Ungulata and Hyraces each one. The London Garden reports that gastric ulcerations occur most often in Carnivora and Marsupialia. Those in the last three orders of our list were small, usually multiple and relatively superficial. The ulcers found in Primates and Carnivora present the usual pictures seen in man. In one example in each of these orders radiating scars of healed defects are mentioned in the notes. None of them seems to have led to cancer, and in only one, a wolf (_Canis lupus_), was the scar tissue sufficient to cause definite impediment to the motility of the stomach. Six of the fourteen examples appeared on the greater curvature, the remainder on the lesser. Ten ulcers were in the pyloric division, the other four being scattered. No other pathology is found common to these cases which might be drawn into etiological association.

TUMORS.

Tumors of the gastric complex are not at all common, there being only the following to report: Primates, Hamadryas Baboon (_Papio hamadryas_), diffuse adenoma; (none in Carnivora with the most ulcers); Marsupialia, Red Kangaroo (_Macropus rufus_), malignant papilloma with metastases. The former tumor, shown in Fig. 17, was a diffuse soft excrescence beginning near the pylorus and stretching along the lesser curvature toward the cardia. Histologically it was made up of glandular acini growing in all directions but always maintaining normal relations of cells and basement membrane. There were no metastases and other reasons for death existed. The tumor of the kangaroo stomach was a true epitheliomatous cancer with metastases to liver, spleen, and kidney. Only one secondary tumor was observed, from a carcinoma of the lung in a Red Kangaroo (_Macropus rufus_).

FIG. 16.—MULTIPLE GASTRIC ULCERS. COMMON WOLF (CANIS LUPUS). CHRONIC
GASTRITIS WITH NUMEROUS IRREGULAR ULCERS OF THE PEPTIC TYPE.
]

FIG. 17.—PAPILLOMA OF STOMACH. HAMADRYAS BABOON (PAPIO HAMADRYAS).
]

THE INTESTINE.

Inflammation of the gastrointestinocolic tube is the most important single condition with which handlers of animals have to deal, and unfortunately it can seldom be diagnosed clinically, early and accurately enough, to make treatment useful. At this Garden some evidence of acute or chronic disease of the tube has been present in 31 per cent. of our autopsies. The reports of other gardens would indicate that their figures might be quite close to this. What is the cause of this high mortality? Incorrect feeding, qualitatively or quantitatively has been put at the top of the list by Plimmer, but he adds other less important factors: Bacteria of infectious power, protozoa, foreign bodies and parasites or their mural cysts. In order to evaluate approximately how each of these acts let us review the causes as they are generally known and later discuss the pathology as seen in the various orders.

(1) Overloading of the stomach by too much food or by rapid eating of a hungry animal is of importance under certain domestic circumstances where times of feeding are irregular or intervals are too long, but this cannot occur in any well regulated menagerie. It is possible, however, that overfilling might occur in certain Ungulata, which have hay and straw nearly always available, if the food in their reach happens to be particularly agreeable or tasty to them.

(2) Insufficient mastication would seem to be important only in those orders which depend upon this action to triturate, insalivate and macerate their food, of which Homo, Primates, Ungulata and Marsupialia are the principal ones.

(3) Disturbance during and after feeding has always been believed to affect digestion unfavorably, and it may be that visitors to a collection exert such an effect; this factor is probably negligible.

(4) The appropriateness of the food is a very important factor in the health of an animal under captive conditions. Diet lists are made up by officials largely according to the known habits and general physiology of an animal, but the food offered can at best only approximate what the wild beast obtains for himself. It does not follow because a selected diet may seem to provide all the elements contained in the food available under natural conditions that it actually does so, especially since we are aware that some essential food factors, known under the term vitamins, are necessary to best development. These substances vary in closely similar foods, and seem to be higher in simple natural foods than in prepared diets. We have seen in this Garden that the inorganic constituents must be correctly represented in the food, else degenerative osseous condition may develop. Inappropriate diet may express itself at once after the receipt of an animal, by its sickness or death, or after some time in the development of chronic tympanites, chronic intestinal catarrh or bony deformities.

(5) The physical condition of food is a matter of no small moment. The taking of soft food in large quantities especially by herbivorous animals, permits too short a sojourn in the gastric fundus and is often followed by pyloric and duodenal disease. Too firm food may pack the rumen, fundus or proventricle as the case may be, and be succeeded by distention of these parts and catarrh of the pyloric and intestinal area. The effect of foreign bodies mixed with food is difficult to evaluate unless of course they be of such a nature (pointed metal and the like) as directly to traumatize the mucosa. Many birds and mammals come to autopsy with a relatively large number of stones and small sticks in the stomach without any distinct evidence that they have been hurt thereby. In the bird the stones may be so large and numerous as to leave little room for food, or small enough to pass out into the intestine where they undoubtedly may pave the way for bacterial action. Smoothly polished pebbles in small quantity seem to have little effect in mammals. Hair balls are not common and unless of large size are apparently unimportant. Considerable sand mixed with food has a distinctly irritating effect. It is perhaps best known as a chronic gastric disorder of horses; we have seen it in zebra.

(6) Spoiled food is obviously a very prime factor in inflammations of the gastrointestinal tract. Its operations are illy understood except perhaps when products of fermentation or putrefaction prevent digestive action or are absorbed. If in small quantities not sufficient to cause acute fermentative inflammation or intoxication, such substances frequently taken may doubtless produce chronic catarrhs. Many animals are fed upon vegetable mashes, or stews which can decompose, while bad meat may occasionally be fed. We had a rather serious outbreak of enteritis in small Carnivora from the use of fowl heads obtained at hotels; some of these cases were shown to be due to B. paracoli, thus to be looked upon as infections. Dirty food while not spoiled may carry with it organisms of decomposition, or of infective qualities, or the dirt may act as an irritative foreign body. We have found that for delicate ungulates (antelopes) it is highly desirable to screen grain, and that the grade of hay should be of the best.

(7) Infectious conditions are of great importance under certain circumstances but with the exception of hog and fowl cholera, the dysenteries and a few other diseases, do not as a rule play a great part in mortality as specific diseases unless of course an epizoötic appear. The greater problem is to understand bacterial action in the face of other factors. Are infectious germs introduced with food and drink in every case of gastroenteritis or do some other factors activate those already present in the gut tract? Unfortunately these questions cannot be answered directly. We can, however, point out which groups of bacteria are most common in some of the orders, which orders are most susceptible to bacterial invasion and which to local lesions with intoxication. The greatest problem in the field is the interrelation of germs of various sorts in the intestinal tract. Certain varieties are known to develop intoxicating aromatic substances, others to elaborate or excrete fatty acids, still others to form antiferments but the conditions existing in the various kinds of intestinal tracts are too little understood to help very much in this study.

(8) Animal parasites have long been considered as one of the causes of gastrointestinal inflammation, a condition largely due to copying from book to book of a few facts and more impressions. The sum of reliable information to-day would seem to indicate that a few parasites—uncinaria being the most conspicuous example of this type—draw considerable blood from the mucosa, that a few, like uncinaria and dibothriocephalus, elaborate an absorbable toxin, that some, notably ascarids, produce an irritating substance, and that many possess the power in themselves or by some excretion to act as antiferments. These factors, were they all combined in one worm, might probably irritate the mucosa sufficiently to produce inflammation, but it is not easy to imagine that they would cause an acute specific condition. It is much more easily conceived that with tiny hemorrhages or ulcerations of mucosæ, bacteria might get in their work or if considerable ferment were neutralized, maldigestion, flatulence or indigestive irritation would ensue. With certain worms like esophagostomum there is considerable evidence to show that a chronic fibrous disease of the intestinal wall arises, but in this case the parasite resides in the mucosa and acts as a foreign body. It would seem, however, that the most important influence that animal parasites exert is to be found in the preparation of the mucosa for the action of bacteria. Masses of parasites may of course physically obstruct the lumen and lead to intestinal stasis and dilatation.

INFLAMMATION.

In analyzing the cause of a gastroenteritis and its consequent effect upon the wall of the tube and upon the viscera, certain physical, chemical and physiological factors must be considered. Whether this may be directly the effect of bacteria or poisons from worms or some other factor seems of little moment since in any fully developed case, symptoms and effects are comparable. Moreover it seems that pathological anatomy, both gross and minute, is essentially the same from Primates to struthious birds, the highest and lowest of the two classes here considered. By this is meant that the acute congestive condition of the gut tract with solution of the surface, to which we have applied the name of toxic enteritis, seems to be met with in this form throughout all the orders. So too catarrhal inflammations are the same to the naked eye and under the microscope, due allowance being made for the fact that mammals use polynuclear cells for exudative purposes while birds employ mononuclears. Concomitantly with these conditions, a degenerative process may be going on in the liver and kidney, and hyperplasias, especially in the true infective processes, will be found in the related lymphatic structures.

The majority of students to-day place responsibility for gastroenteritis upon the bacteria known to be present in the various intestinal tracts, mentioning especially colon and proteus groups, streptococci, the necrosis bacillus and anaerobes of the Welch class. In a few of our studies of intestinal bacteria in cases of enteritis one thing has been very definite and that is that in the intestinal content of animals whose food is largely meat, Gram-negative bacilli have predominated, whereas in herbivorous animals Gram-positive organisms have been most numerous. From the observations of Kitt, Strassberger and some others, the normal flora of domesticated animals is subject to wide variations so that our observations must receive confirmation before they are finally acceptable. We have on several occasions isolated from carnivorous intestines Bact. paracoli, Bact. suipestifer and other members of this group. We have no reliable cultural data upon the herbivorous intestine and can only quote the Gram pictures as mentioned above. On two occasions, an eland and an elk, a very large number of forms corresponding to necrosis bacillus were seen; to this organism Kitt gives considerable power in the production of necrotizing processes.

TABLE 11.

_This table shows an analysis of all cases of gastroenterocolitis. The left half of the table is an analysis of orders upon which one hundred or more autopsies have been done, the right half of orders with fewer than that number. The left half is expressed in percentages, the right half in number of cases only since percentages might be misleading. Left hand table: First column is percentage of gastroenterocolitis per order; next five columns the percentages in which each of the factors in the headings was believed responsible; the last three columns show the participation of each of the divisions of the intestinal tract; thus Primates had all told 24.8 per cent. of inflammations of which 7.2 per cent. were in stomach, 18.3 per cent. in the intestines and 8 per cent. in the colon; obviously many had all three sections affected. Right hand table is constructed on a similar basis except that number of cases is quoted, not percentages, and the total is put in the last column._

════════════╤═══════════════════════════════════════════════════════ │ Percentages in orders with sufficient autopsies. ────────────┼─────────┬────┬────────┬─────────┬────────┬──────────── │Per cent.│Food│Bacteria│ Animal │Physical│Undetermined │ of │ │ │Parasites│Objects │ │Autopsies│ │ │ │ │ ────────────┼─────────┼────┼────────┼─────────┼────────┼──────────── Primates │ 24.8│ 1.8│ 4.4│ 3.6│ │ 15. Lemures │ │ │ │ │ │ Carnivora │ 46.1│ 2.9│ 7.2│ 5.8│ .2│ 30. Pinnipedia │ │ │ │ │ │ Insectivora │ │ │ │ │ │ Chiroptera │ │ │ │ │ │ Rodentia │ 25.│ 5.│ 2.│ 2.│ │ 16. Ungulata │ 24.8│ 6.6│ 2.2│ 2.│ .8│ 13.2 Proboscidea │ │ │ │ │ │ Hyraces │ │ │ │ │ │ Edentata │ │ │ │ │ │ Marsupialia │ 33.1│ │ 10.│ 10.1│ │ 13. Passeres │ 23.6│ .1│ 4.5│ 1.8│ .15│ 17. Picariæ │ │ │ │ │ │ Striges │ 41.5│ 1.5│ 5.3│ .7│ │ 34. Psittaci │ 36.6│ .3│ 10.7│ 3.7│ .15│ 21.8 Accipitres │ 40.7│ │ 4.5│ │ .5│ 35.7 Columbæ │ 17.8│ │ .6│ 3.│ .6│ 13.5 Galli │ 38.6│ │ 5.3│ 19.6│ │ 13.7 Hemipodii │ │ │ │ │ │ Fulicariæ │ │ │ │ │ │ Alectorides │ │ │ │ │ │ Limicolæ │ │ │ │ │ │ Gaviæ │ │ │ │ │ │ Impennes │ │ │ │ │ │ Steganopodes│ │ │ │ │ │ Herodiones │ │ │ │ │ │ Odontoglossæ│ │ │ │ │ │ Palamedes │ │ │ │ │ │ Anseres │ 29.6│ .3│ 4.4│ 2.3│ .6│ 22. Struthiones │ │ │ │ │ │ Crypturi │ │ │ │ │ │ ────────────┴─────────┴────┴────────┴─────────┴────────┴────────────

════════════╤════════════════════════╤════════════════════════════════ │sufficient autopsies. │Number of cases in orders with under 100 autopsies each. ────────────┼───────┬──────────┬─────┼────┬────────┬─────────┬──────── │Stomach│Intestines│Colon│ │Bacteria│ Animal │Physical │ │ │ │Food│ │Parasites│Objects │ │ │ │ │ │ │ ────────────┼───────┼──────────┼─────┼────┼────────┼─────────┼──────── Primates │ 7.2│ 18.3│ 8.│ │ │ │ Lemures │ │ │ │ │ 8│ 2│ Carnivora │ 21.│ 41.│ 6.6│ │ │ │ Pinnipedia │ │ │ │ │ 1│ 1│ 1 Insectivora │ │ │ │ │ │ │ Chiroptera │ │ │ │ │ │ │ Rodentia │ 7.│ 20.5│ 3.5│ │ │ │ Ungulata │ 9.1│ 20.│ 2.5│ │ │ │ Proboscidea │ │ │ │ │ │ │ Hyraces │ │ │ │ │ │ │ Edentata │ │ │ │ │ │ │ Marsupialia │ 22.│ 21.│ 3.5│ │ │ │ Passeres │ 1.2│ 22.│ 3.│ │ │ │ Picariæ │ │ │ │ 1│ 10│ 4│ Striges │ 6.│ 40.│ .7│ │ │ │ Psittaci │ 1.7│ 35.4│ 1.3│ │ │ │ Accipitres │ 5.2│ 39.│ 1.│ │ │ │ Columbæ │ 4.5│ 13.5│ .7│ │ │ │ Galli │ 2.6│ 21.6│ 19.6│ │ │ │ Hemipodii │ │ │ │ │ │ │ Fulicariæ │ │ │ │ │ 6│ 1│ Alectorides │ │ │ │ 1│ 1│ 2│ Limicolæ │ │ │ │ │ │ │ Gaviæ │ │ │ │ │ 1│ 1│ Impennes │ │ │ │ │ │ │ Steganopodes│ │ │ │ 1│ 1│ │ Herodiones │ │ │ │ │ 1│ 3│ Odontoglossæ│ │ │ │ │ │ │ Palamedes │ │ │ │ │ │ │ Anseres │ 2.5│ 27.7│ 6.6│ │ │ │ Struthiones │ │ │ │ │ 7│ │ Crypturi │ │ │ │ │ │ │ ────────────┴───────┴──────────┴─────┴────┴────────┴─────────┴────────

════════════╤═════════════════════════════════════════════════════ │Number of cases in orders with under 100 autopsies each. ────────────┼────────────┬───────┬──────────┬─────┬─────────────── │Undetermined│Stomach│Intestines│Colon│ Total Animals │ │ │ │ │ Showing │ │ │ │ │Gastroenteritis ────────────┼────────────┼───────┼──────────┼─────┼─────────────── Primates │ │ │ │ │ Lemures │ 13│ 4│ 19│ 3│ 23 Carnivora │ │ │ │ │ Pinnipedia │ 8│ 7│ 8│ 1│ 11 Insectivora │ │ │ │ │ Chiroptera │ 2│ 1│ 1│ │ 2 Rodentia │ │ │ │ │ Ungulata │ │ │ │ │ Proboscidea │ 1│ │ 1│ │ 1 Hyraces │ 2│ │ 1│ 1│ 2 Edentata │ 2│ │ 1│ 1│ 2 Marsupialia │ │ │ │ │ Passeres │ │ │ │ │ Picariæ │ 24│ 5│ 36│ │ 39 Striges │ │ │ │ │ Psittaci │ │ │ │ │ Accipitres │ │ │ │ │ Columbæ │ │ │ │ │ Galli │ │ │ │ │ Hemipodii │ │ │ │ │ Fulicariæ │ 8│ 1│ 15│ │ 15 Alectorides │ 10│ 2│ 13│ 3│ 14 Limicolæ │ 1│ │ 1│ │ 1 Gaviæ │ │ │ 2│ │ 2 Impennes │ 3│ 1│ 3│ │ 3 Steganopodes│ 8│ 1│ 10│ │ 10 Herodiones │ 25│ 1│ 24│ 6│ 29 Odontoglossæ│ │ │ │ │ Palamedes │ 1│ │ 1│ │ 1 Anseres │ │ │ │ │ Struthiones │ 14│ 8│ 20│ 3│ 21 Crypturi │ 1│ │ 1│ │ 1 ────────────┴────────────┴───────┴──────────┴─────┴───────────────

THE TABLE.

Our records have been analyzed from the standpoint of diagnosis and the most probable cause. The first will be taken up in discussing each of the orders. The probable causes are divided into food, bacteria, animal parasites, physical objects and undecided, in other words a classification based upon the most prominent or definite evidences as seen at postmortem combined when possible with antemortem observations. When findings were inconclusive or contradictory, cases were called undecided, naturally a very large group. Fermentative processes in the presence of obviously undigestible material, are classified with food as a cause. When evidences of septicemia existed in absence of the other factors, it is held that bacteria were responsible. Cases were grouped under animal parasites when these were the most definite findings. Physical objects are relatively unimportant and self-explanatory. To the etiological chart there are appended columns intended to show the percentage or case incidence of the disease of the grosser subdivisions of the gastrointestinal tract which indicate in a general manner what part of the tube in the various orders is most susceptible to disease. While of course conclusions must be drawn with great caution, there can be little doubt, for example, that carnivores and marsupials have more gastric disease than any other order, and that the high place for the colon is held by the gallinaceous birds. This charting was suggested by the work of Dr. Raymond Pearl upon statistics, wherein he takes as a basis of classification the part of the body which succumbs to disease- producing organisms or from which a disease starts. It cannot be stated that there is a clear cut relationship between enteritis and the expectancy of life.

MAMMALIA.

The PRIMATES as an order have their share of inflammations of the gastrointestinal tract and present points of interest. Acute digestive disorders succeeded by acute dilatation of the stomach, or in less fermentative cases by acute catarrh of the intestine, are not at all uncommon. The reason for this is not discovered by reviewing the diet and manner of feeding. The buccal pouches, distensible esophagus, the freely movable stomach, and relatively elastic gastric wall would seem to permit of very considerable dilatation to accommodate the large quantities which the monkey sometimes crams into himself. Nine fairly acceptable records of gastric overfilling exist and two of them seem to have been followed by tympanites sufficient to embarrass respiration, in one case there occurring an acute cardiac dilatation with myocardial degeneration. The animals give no symptoms of this condition and in the last case cited the beast, while old, ate well and was not distended the evening before death.

When acute gastritis exists (twenty cases) the animal seems uneasy but does not vomit. On one occasion I was called to see a monkey which was retching and seemed in pain. Lime juice was offered and taken, followed by gentian and cardamon, which seemed to give some benefit. Somewhat later this was repeated in another case, but observations where this might be useful are rare.

The pathology of gastric conditions offers little to contrast with that of man. The enormous distensibility of the fundal pouch often suggests to the observer the rumen of ungulates. Acute gastritis of one kind or another and acute catarrhal enteritis are the most common lesions noted in the Primates. Involvement of the intestine or colon need not carry with it an increase of signs of illness, although at times one will see an evidently sick animal with diarrhœa. Anatomically the lesions are commonly restricted to the stretches of gut _above_ the ileum, it being rather rare that this division or the colon is affected. Pathologically the lesions are catarrhal with definite involvement of the follicles in about one-third of the cases. In this order toxic and pseudomembranous forms are quite rare and ulcerative lesions uncommon. Colonic disease as a sequel to inflammation higher up is sometimes seen in the follicular varieties, but takes a minor place compared to amœbic dysentery of which we have had several cases; this will be discussed under a separate heading. Degenerative disease of the skeleton is almost always accompanied by a low grade of enteritis but not necessarily gastritis or colitis. The pallor of the mucosa, while at times striking, may be relieved by follicular spots and petechia or pigmentation. Often, however, animals suffering from osteomalacia and rickets come to their end by an acute inflammation of the gut tract.

The bacteriology at our disposal allows no conclusions. Aside from a case probably due to Ps. fluorescens and one with colon bacillus abscesses in the liver, no reliable data are at hand.

Reference to Table 11 reveals the fact that among orders with sufficient autopsies to permit percentages, the alimentary tract in monkeys is in the group of low figures, that the intestinal section is relatively more often affected, and that the colon is more often diseased than in other mammalian orders, and is exceeded only by the gallinaceous birds.

The LEMURES, of which we have eighty-six autopsies, do not differ much in anatomy from the Primates, however greatly they disagree in habits and outward appearance; their diet is the same. Clinically the slothful behavior of a normal lemur probably obscures symptoms and signs of illness, for our antemortem notes with the exception of a few observations of loose stools, fail to offer a lead as to diagnosis. This order has a large incidence (twenty-three cases) of gastroenteric conditions as shown in Table 11, but some explanation of the figures is deserved. In the first place, only one case of acute gastritis occurred, and this was apparently a part of a general infection, and if induced at all by food this was only secondary. Indeed as one reviews the records it does not seem that the lemurs are easily disturbed in their gastric digestion. Acute and subacute inflammations from bacterial action seem definitely more prominent since they take the catarrhal, follicular and deep submucous form and are frequently associated with generalized infectious processes. One amœbic case was observed and there was another in which a heavy cestode and nematode infestation seemed to have paved the way for bacteria.

CARNIVORA.

The food of this order is received into the fundal part of the stomach, the distensible but normally capacious left and superior two-thirds of the organ. The general shape of the viscus, that of a gourd, permits a fairly sharp separation of the fundal and pyloric sections, so definite indeed that the pathology of the two parts was studied. The intestines vary in length, but in the land carnivores are relatively short, narrow in lumen and rich in wall. A cecum, or at least a blind end of the large gut made by the insertion of the small intestine above the tip of the colon, is suggested in all families, although, as in the bears, it may be quite insignificant or rudimentary. Theoretically no stasis should occur at this point. The colon is short in all carnivores and, like the small gut, with a heavy wall. The comparative simplicity of the carnivorous gut tract, the ability of many of these animals to disgorge, the suggestion of high resistance of the upper end of the tract to infection and the ease with which diarrhœa can clear out the tube, would seem to warrant the expectation that inflammation would not be serious. Such, however, is not the fact for, on the contrary, they have shown a higher incidence than any other order for which we have adequate comparison. Anatomically considered their stomach occupies the second place in vulnerability, next to the marsupials, and their intestines the highest place; this indicates of course that combined gastric and intestinal disease has often occurred. Involvement of the colon occupies the second place, in ordinate susceptibility, being exceeded only by the monkeys, due to heavy parasitic infestation, but would occupy the first place were the eleven amœbic dysenteries in monkeys subtracted from their total, a subtraction which might be allowed since it represented an epizoötic outbreak.

Etiologically considered, it would seem as if the influence of incorrect feeding were of little importance, and from one standpoint this is probably the case. Acute fermentative or irritative processes are not common at all, while more inflammatory pictures, catarrhal, erosive or ulcerative, are the rule. There is another phase to the term incorrect food, that is incorrect in its cleanness. During 1912–15 there was an increasing mortality among the cats and dogs fed upon horse meat, mutton and fowl heads. Early in 1916 the butcher shop was reconstructed and thoroughly cleaned and covered galvanized pans supplied in which to transport the food; these pans were scrubbed and scalded after use. Since that time, infections inflammations of the stomach and intestines have shown an ever increasing downward incidence, which result, there having been no material changes in other directions, I do not hesitate to ascribe to the improvement of butchering and dispensing engineered by Dr. W. B. Cadwalader.

Helminths seem to be of importance in this order both by reason of the percentage of autopsies in which they presented the most probable or at least most suggestive cause and because uncinaria and strongylus have been seen attached to the wall and a large bulk of known irritative cestodes have occupied the lumen. Physical objects, stones, bones, wire, may cause irritation enough to activate bacterial action or may actually penetrate the wall; the latter action is well known. In so far as practical application of this is concerned, it teaches to feed whole, unsplintered or ground bone.

The distribution and character of pathological lesions according to the region of the stomach is what might be expected from the shape and physiology of its parts. True inflammatory processes are best, and in some cases only seen in the pyloric half of the viscus, while the changes in those few cases believed to be fermentative or irritative in nature were largely confined to the fundus. Dilatation of the latter part may be understood because there the muscular coats are about equal to the mucous in thickness and one-half the width of those at the pylorus, but why inflammatory processes should not be so developed in the fundus is not clear unless the greater availability of mucus protects the secreting wall. Not only does acute inflammation reach its most definite form in the second part of the stomach, but the irregular pigmentation, mammillated overgrowth and atrophy or ulceration of chronic disease are likewise best seen in this part.

Acute enteritis, of all varieties, is seen more beautifully in carnivores than in any other order of mammals, and nowhere can it be studied better. Its gross appearance is that of the text-book and its minute character even more instructive. I have used a slide of acute catarrhal enteritis in a lion for the illustration of this lesion for the _Text-book of Pathology_ by Doctor Stengel and myself. However, as is known to all who have paid any attention to enteritis, the postmortem findings are usually much less definite than clinical observations would warrant one to expect. The Carnivora not uncommonly show intestinal congestion, mucous membrane swelling without edema or opacity, congestion of the spleen, cloudy swelling of the liver and kidneys and perhaps mesenteric lymph node edema. This picture we have viewed as a toxic affair of some sort or a bacterial infection not yet far enough advanced to produce catarrhal or ulcerative enteritis and septicemia. In such cases the carnivorous intestinal mucosa offers instruction. The epithelium is vacuolated or fringed on the free edge or may be missing altogether. In the depths mucus formation is very active, and where it is going on, round cells seem attracted, collecting in groups in the villus or in the subjacent submucosa. Perivascular round cell increase may be noted. Plasma cells and granular eosinophiles are common, but I cannot state how important the latter are in the general picture because of the frequency of parasites in carnivores. The central vessel of the villus and the arterioles of the submucosa are injected. Lymph follicles may or may not be enlarged, but if so usually fail to show a germ centre.

Colitis alone is not common in this order, but as an extension process or involvement at the same time as the upper levels it occurs occasionally. The only fact I wish to record and one which I would emphasize because of having seen it recently in a human case of chronic colitis, and since it does not appear important to systematic writers, is superficial blood supply. The capillary network of the colonic villi, while rich, is in the form of a fine plexus just under the epithelium. In the cases studied these vessels become quite distinct and possess much more definite walls, often bordered by mononuclears, while connective tissue is more evident at the bases of the villi and deeper. This may help in deciding the existence of a colitis.

Bacteriologically the most instructive experience to report is the discovery that a small outbreak of enteritis among small Carnivora, chiefly cats, fed upon fowl heads was due to Bact. paracoli, or at least this organism was found in the intestinal mucosa, spleen, and heart’s blood of three cases. The type of enteritis was hemorrhagic and follicular. There was also a case of septicemia apparently emanating from enteritis due to Bact. suipestifer in a lion (_Felis leo_). These facts bring strongly to attention the modern teaching that meat poisonings of the Gärtner type are to be considered as infectious and not of the so-called ptomaine group.

PINNIPEDIA, while related closely to the Carnivora, are grouped in a suborder in our classification and because of their restricted diet are treated here in a separate paragraph. The tract is peculiar in the strong tubular stomach sharply bent upon itself, the great length of the small gut (upwards of a hundred feet in some genera), and the practical absence of a cecum. Pathologically speaking, the most striking lesion of these animals is ulcerative gastritis, a process usually most marked along the posterior-superior surface, but not confined thereto. Upon inspection the gastric mucosa, normally supplied with low regular rugæ, is much distorted by swellings upon the top of which are irregular ragged ulcers with rounded elevated but not frayed margins. The density of the edges indicates much infiltration of the deep mucosa and submucosa; this can be confirmed by microscopical examination. One attempt to study this gastritis bacteriologically was fruitless. Sections of one case showed streptothrix-like masses while in another case bacterial colonies and yeast-like bodies were found in adjacent lymph nodes. The genesis of this condition might lie in injury by fish fins or by foreign bodies, of which large numbers are found at times (a pint and a half of stones, marbles, and sticks were found in one stomach). Gastritis has been the starting point of septicemia on two occasions, and three times an acute exacerbation or new implantation of infection occurred, with extension into the intestine. It is interesting that all the deaths of Pinnipedia with gastroenteric conditions occurred in the winter months.