Part 17

One cannot speak so definitely of pleuritis in birds since this tissue merely represents in them the covering of the lung and is firmly attached posteriorly to the ribs and anteriorly to the air sacs. Exudates show as collections upon the air sac side of the combined membrane, pleuritis proper in birds being an infiltrative affair coming through the pulmonary tissue and therefore being a part of pneumonitis. I notice a tendency in a few articles to write of pleuritis when the process is confined to the thorax but this gives the impression that the disease is peculiar. There seems no difference in the gross and minute appearance between thoracic serositis and panserositis. The course of procedure seems to be from the anterior or mesial pulmonary ostia into respectively the cervical and thoracic air sacs and this seems to hold good whether the infection be mycosis or fowl cholera or fowl pest. There are records of 104 cases of serositis in birds of which 45 were among parrots, the remainder being well distributed among the various orders; only two each occurred in Galli and Anseres, orders prominently affected under domestication. This high percentage of pleuroperitonitis among parrots and their congeners can only be explained upon the ground of a continued infection of our stock by the virus of fowl cholera and by mould. One case of undoubted fowl cholera occurred recently and as the records are reviewed a few are discovered where the organism was found. The virus must be of low grade for we have had no severe and devasting epizoötic. Mycosis is constantly with us no matter what we do in hygienic measures. There was a small group of cases of pulmonary and serous membrane mycosis combined with staphylococcus infection which carried off six birds. The pathology of this group was interesting because one could follow the infection of the bacterium. The anterior pulmonary ostium was surrounded or covered by a mycotic mass and spreading downward from this was a grayish yellow turbidity of the air sac walls with a delicate sticky or almost mucilaginous exudate extending into the lateral abdominal and posterior sacs.

There is on record one tumor of the pleura, an endothelioma, in a Clouded Leopard (_Felis nebulosa_). It was the usual plate-like thickening with warty excrescences. No metastases occurred. (Figs. 12 and 13).

SECTION VII THE ALIMENTARY TRACT. PART 1.—PHARYNX, ESOPHAGUS, STOMACH AND INTESTINES

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.

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.

GASTRIC ULCERS.