Part 40

Diabetes is an infrequent but well recognized disease among domestic animals. Its detection depends on a rather vague chain of symptoms confirmed by the discovery of sugar in the urine. For the suspicion that a wild animal was suffering with diabetes one would have to rely upon great thirst, loss of flesh, depression, excessive urination and possibly cataractous opacity of the eye. Such a chain of symptoms has not been detected. At every occasion at postmortem that the bladder is full of urine, a routine examination is made. In this way we detected one case which seems to have been diabetes, the diagnosis being based upon the glucosuria and the lipemia. For some unknown reason a section of the pancreas was not made, a regrettable matter since a definite purulent gingivitis existed and may have lain at the basis of an infective pancreatitis, well known to be the cause of certain cases of diabetes. The case is recorded in full since it is unique, no other case in a wild animal being fully reported.

The arctic fox (_Canis lagopus_) ate and appeared well the day before it was found dead. Diagnosis—Diabetes mellitus. The animal was in good condition. The left conjunctiva was reddened, congested, edematous, with slight mucopurulent discharge in canthus. Muscles have a cloudy appearance. Fat lacks rich yellow color. The general impression of anemia is present. Lungs and pleura are normal throughout. Heart muscle is pale, firm and tough. The tricuspid shows thickening of the edge of posterior leaflet, the mitral shows slight sclerosis of edge of mesial leaflet. The auricles are distended with clot. Left ventricular wall is greatly thickened. Upon incising the heart the surface of blood shows fine fat globules. Peritoneum is normal. Liver is slightly increased, surface smooth, edges rounded, consistency soft, color brownish red with yellow mottlings which are without definite boundaries; the section surface is moist, granular and opaque. The bile is fluid, green-yellow and the duct is patulous. The spleen is slightly enlarged and soft. The kidney is slightly enlarged, capsule strips easily leaving a smooth, purplish red surface; section surface is glistening, moist and exudes blood; consistency is slightly softened; cortical striæ very distinct. The bulging cut surface and poor demarkation of cortex and medulla characteristic of acute nephritis are present. The organ shows fat globules in the expressed blood. The adrenals are very small, firm, brown, bean-shaped bodies with a brownish medulla. The bladder is slightly distended with turbid urine. Urine shows dark granular casts, compound granule cells, spermatozoa and a positive Fehling’s test. Prostate is large and firm and a turbid material exudes from external meatus. The mouth shows several decayed teeth. In the neighborhood of last molars on left side of upper jaw a bead of pus exudes; further pressure results in no greater flow. The stomach is distended with a great quantity of undigested food and gas; no worms. Serosa and wall normal but anemic. Duodenum normal. Jejunum contains numerous worms about 1 to 1.5 cm. long; it is distended with gas. The pancreas is large, soft, like fat, white; it extends between the layers of mesentery along the course of the duodenum; at first the pancreas was mistaken for fat.

HISTOLOGICAL NOTES.—Spleen shows a distinct overgrowth of trabeculæ. Beyond this there is nothing pathological. Liver shows distended portal venules in which there are chains of bacilli. There is no especial fibrous overgrowth of capsule of Glisson; capillaries are choked with shadow corpuscles and here too, long chains of bacilli may be seen; parenchyma cells show postmortem change. Adrenal is the seat of postmortem degeneration, not congested, nor is there any evidence of bacterial invasion. The kidney shows no interstitial changes, in fact the section seems to be entirely normal save for moderate congestion. Vessels show no bacteria.

SECTION XV THE RELATION OF DIET TO DISEASE

BY

DR. E. P. CORSON-WHITE

Food in the widest acceptation of the term, means every thing ingested that goes, directly or indirectly, to growth, repair of the body, or production of energy, all of which phenomena must continue when food is withheld or supplied in insufficient quantities. Under the latter condition the processes go on at the expense of the body tissues as these are protected only when the diet is adequate in every way. A proper diet, therefore, must be one on which an animal will attain maximum development, maintain a normal weight curve, show a minimum susceptibility to disease, live out a full term of life, breed normally, and rear healthy offspring, capable of normal independent life after they are weaned. It must fulfill the caloric needs of the body, and in young animals it must also supply the growth impulse. In its physical properties it must fit the morphological demands of each type of gastrointestinal tract. In its chemical content it must supply all the elements found in the body in usable form, and in amounts sufficient to cover the needs of the body for growth, repair and waste. To evaluate fully the influence of food on the individual animal it is necessary to study its relation: (1) to the type of alimentary tract, (2) to the type of bacterial flora and their metabolic processes, (3) to the chemical needs of the body, (4) to the changes arising in the catabolism and anabolism of all types of food, (5) to exercise or its lack, keeping in mind always the constant interdependence of all factors. Our knowledge of nutrition has to a very large extent paralleled the advances in chemistry, especially the researches into the structural makeup of living cells, the intermediate stages in their upbuilding and degradation and the products resulting from their physiological activities.

Incorrect feeding both qualitative and quantitative undoubtedly plays an important rôle in producing disease. In the early works on nutrition, the proportion of fats, carbohydrates and proteins was regarded as the essential point of a normal diet. The researches on the composition of foods marked the first real epoch in this history and Fischer’s[57] studies on the variation in the composition of proteins from different sources first introduced the idea of quality. Later Mendel and Osborne investigated the biological values of purified proteins, while at the same time McCollum and others were studying the value of the groups of proteins occurring in a single natural food stuff, were calling attention to the so-called vitamines, and were emphasizing the need of balanced inorganic materials. These studies have practically revolutionized our knowledge, particularly of the effects of badly balanced foods. They have clearly demonstrated that dietary values can, in all probability, be discovered only by careful biological study of feeding experiments together with the finer analysis of the components of the diet, especially of the protein and fat radicles. At the same time a definite appreciation of the rôle of each element in metabolism must be kept in mind.

These varied studies on nutrition have shown that the chemical requirements of a diet are in their ultimate analysis essentially the same for all species of the higher animals—that is all require approximately the same amount of protein, fat, carbohydrate, etc., per kilo of body weight, while the morphology of the tract decides the physical properties of the diet.

RELATION OF FOOD TO ALIMENTARY TRACT.

Food derived from animal sources is high in protein, readily digested, and highly putrefactive. This type of diet is suited to an alimentary tract which permits rapid passage through its length, and is fitted with sturdy walls. The gastric section is simple, the intestine short and narrow with ill-defined separation of its parts into small gut, cecum and colon. This type is found in all land Carnivora. The fish-eating carnivores have a strong tubular stomach and an enormous length of intestine, but no cecum. The omnivores occupy a middle place. In them the alimentary tract consists of a simple stomach, a short wide intestinal tube, and a more complex, although still comparatively simple, cecum which is generally longer than that found in the carnivores. This tract is too small to manipulate the bulky vegetable masses necessary to provide their minimum protein requirement, and too long and complicated to dispose quickly of the putrefactive animal tissue. Among these animals colitis is common, due to the fact that the shape and position of this part of the tract favors stasis, or at least a sluggish movement of its contents at a point in the digestive scheme where the food residue is rich in protein by-products, ready for bacterial growth.

The herbivores with food derived from plants which requires a long period of time for its digestion, have, on the other hand, voluminous stomachs, or large ceca or both; and very long small intestine. In this tract the concentrated food of the carnivores would provide an enormously excessive protein intake or if only the protein requirement is supplied would leave the tract so empty that it would be unable to functionate.

All studies in comparative anatomy demonstrate the fact that while neither a complex stomach nor a large cecum is essential to the digestion of vegetable food, a capacious and complex alimentary canal, as a whole, bears a relation to vegetable diet, particularly in the mammals. Either a highly developed concentrated glandular apparatus is added to the stomach, as in the wombats, beavers and dormice, or the stomach is subdivided, sacculated, or otherwise amplified as in the ruminants and herbivorous marsupials. Sometimes both complexities are combined as in the case of the sloths. If the simple stomach is retained, it is supplemented by a large sacculated colon or cecum, as in the horse. In birds, the proventricle is larger in meat- and fish- eaters, while the gizzard is more muscular in grain- and insect-feeders, and the intestines are longer in those devouring coarse green grass and leaves. The length of the ceca is related entirely to the diet, the long ones corresponding to the diet which needs protracted periods of time to exhaust its nutriment.

THE BACTERIAL FLORA.

The bacterial flora harbored in the intestinal tract is closely related to the type of food and to the character of the alimentary tract. Levin[58] found sterile intestinal tracts in white bears, seals, reindeer, eider ducks and penguins when in the Arctic regions; but these same animals when they are brought to a temperate climate rapidly acquire intestinal bacteria. The function of the normal inhabitants of the tract is, probably, to protect the body against invasions of obnoxious species. Herter found in man that a few species adapt themselves to the digestive tract and control the growth of newcomers capable of doing injury. These common varieties become a source of danger only when present in large numbers.

Bacteria which produce decomposition of food in the digestive tract are of three types: (1) Pure putrefactive anaerobes, (2) organisms both fermentative and putrefactive, but tending generally to antagonize the putrefactive anaerobes, and (3) fermentative organisms. In the stomach, fermentation of carbohydrates with the production of organic acids is a frequent occurrence. Putrefactive types are very rare except with pyloric stenosis, a condition which favors excessive fermentation by diminishing the tone and motility of the stomach and the amount of hydrochloric acid. This condition is further increased by excessive carbohydrate food. In general the products of fermentation tend to restrict putrefaction, yet both may be operative. In the small intestines, bacteria are always present because of the protein richness of secretions, the rapid digestion of food and the slight or ineffectual antiseptic properties of intestinal juice, bile and pancreatic secretions. The putrefactive bacteria rapidly increase and decompose any protein that is unabsorbed—a process most marked in the colon because its shape and position favor stasis or slow movement of its contents. In general the greater the amount of unabsorbed and digestible protein and the longer the material stays in the intestinal tract, the greater the putrefaction. The meat-eating animals develop Gram-negative bacilli, while the carbohydrate-eaters show a predominance of Gram-positive types.

Ingested food never contains the enormous amount of bacteria found in the feces. The alimentary tract with its contents forms a most efficiently combined incubator and culture medium, in which bacterial growth exceeds that of any known location both in intensity and complexity. The range of reaction and composition of nutritive substances at different levels of the intestinal tract is such that a great variety of bacteria capable of growth at body temperature develop. The prominent types that appear in the flora of each order of mammals are fairly constant in their occurrence. They depend primarily on food ingested, and show well marked seasonal variations, dependent again on changes in food. Faulty feeding may itself give rise to a toxic condition of the gastrointestinal tube, and thus often prepares this soil for the development of organisms.

The intestinal flora also changes along rather definite lines as the diet of the host changes from the monotony of the infant to the variety of the adult. At birth the tract is sterile, but bacteria soon make their entry through the mouth in food and water. The majority of these organisms pass to the stomach where many are destroyed, but a number travel to the intestines where they may gain a foothold. There is always a mechanical transportation of intestinal bacteria from higher to lower levels. A continued preponderance of protein in the diet of all animals leads to a partial or complete suppression of the Gram-positive acid- forming groups and an increase of the proteolytic Gram-negative types; while on the other hand an excess of carbohydrate leads to diminution or suppression of proteolytic activity and an increase in the fermentative organisms. Therefore the most important normal factor in determining the intestinal flora in health is the chemical composition of the ingested foods.

The nature of the dominant organisms which develop in diets rich in carbohydrates varies with the carbohydrate itself. In all ordinary diets there are (1) starches—forms not readily fermentable, and (2) sugars— which are largely absorbed from the higher levels of the small intestine, leaving residual starches and proteins in relatively great concentration in the lower levels. Therefore the obligate fermentative organisms are prominent only in the higher levels, the facultative appear in the intermediate places, and the obligate proteolytic organisms in the lower intestines. This accounts in a measure for the great increase of lower intestinal disturbances in omnivores. Complete proteins resist putrefaction, but the products of protein digestion and of the intestinal secretions constitute the main substrata for putrefactive bacteria. Animal protein develops more active proteolytic bacteria than vegetable protein, which accounts for the greater predominance of putrefactive infections in carnivores than in omnivores.

There are two important factors to consider in discussing the influence of diet on intestinal bacteria: (1) The substitution of types, which frequently follows a monotonous diet, and (2) the change in metabolism of existing types of bacteria when dietary conditions are such that the intestinal medium at one or another level fluctuates in its content of usable carbohydrate and other nutrient. The nature and extent of these modifications and their effects upon the host vary greatly, not only qualitatively but quantitatively. An invasion of the tract by exogenous bacteria, as the dysentery bacillus, cholera, typhoid, etc., in food or water may lead to a more or less pronounced replacement of some of the normal intestinal types by these alien organisms, and to the production of disease.

The importance of all the foregoing facts concerning the changes in the food, in the intestinal cultural substrata and in the advent of new kinds of organisms was emphatically demonstrated in the marked fall in gastrointestinal diseases in carnivores after proper screening of meats. The simple protection of the food given to these animals eliminated the air bacteria which, entering from dust and flies, alter the chemistry of the meat before consumption or change the flora of the intestine after consumption. Normal organisms, or types indistinguishable from them, may multiply, through unusual conditions, extend their normal habitat, and eventually lead to abnormal reactions detrimental to the host. These facts throw considerable light on the site and character of gastrointestinal lesions found in various orders, a subject to be discussed more fully later.

There are many intestinal disturbances of unknown causation, in some of which bacteria presumably play a secondary part. The primary disturbance is due to the products resulting from the action of bacteria upon food. Many toxic bodies are produced either before or after ingestion by the bacterial decomposition of carbohydrate, fat or protein, independent of any actual infection. The symptoms arising from bacterial decomposition of foods depend largely on the organism concerned and vary from a mild intoxication to a severe toxemia.

RELATION OF DIETARY GROUPS TO AUTOPSY DIAGNOSES.

Analysis of the autopsies on file from sole point of view of dietary habits of the animals gives rather interesting groupings of disease states, which apparently and, in some cases definitely, emphasize the relationship between food, metabolism and disease. (Table 19.)

From this table a few facts stand out prominently. It is definitely shown that both birds and mammals on a diet of mixed animal and plant tissue show a low percentage of disease in the gastrointestinal tube, liver, pancreas and kidney. The mammals on this diet give the highest figures for anemias and degenerative osseous conditions. Birds on this diet show very little osteomalacia, but a fair amount of anemia. Possibly this may be accounted for by the fact that all of them pick gravel and may be able from this to supply some of the inorganic deficiency. Carnivorous birds and mammals, on the other hand, show an exceedingly large assortment of gastrointestinal disorders, diseases of the accessory glands of digestion, and of the kidneys. Disorders of the thyroid gland are almost entirely confined to carnivorous mammals—7.5 per cent., compared to 0.25 per cent. in all other orders. Gout, while common among birds, was not present in any mammalian autopsy, while arthritis in mammals reached its highest record among grass- and grain- eating herbivora. The percentage of rickets was highest in the young carnivores (2.6 carnivores as against .4 per cent. in all other mammals), and was very rare among all birds.

The succulent vegetable diet was lowest in its relation to degenerative visceral disorders and highest in acute gastritis; the latter fact was probably due to the fermentation of soft moist food that requires rather a long time for its primary digestion. This type of food has also a high and easily available sugar content which makes it a very favorable medium for many of the fermentative types of bacteria. Most of the lesions in this group were around the pylorus and upper duodenum.

TABLE 19. _An Analysis of the Pathological Findings Described in the 5,365 Autopsies from the Point of View only of the Dietary Habits of the Animals. The Percentage Results Represent the Proportionate Number of Cases of Each Pathological Lesion Found in the Entire Group of Animals on Each Special Diet without Reference to Zoological Orders._ ═════════════════╤═══════════════════════════════╤═══════════════════════════════ Disease states │ Mammalia 1860 │ Aves 3505 ─────────────────┼──────┬───────┬────────────────┼──────┬───────┬──────────────── „ │Omniv-│Carniv-│ Herbivora │Omniv-│Carniv-│ Herbivora │ ora │ ora │ │ ora │ ora │ ─────────────────┼──────┼───────┼──────────┬─────┼──────┼───────┼─────┬────────── „ │ „ │ „ │Succulent │Grain│ „ │ „ │Seeds│Succulent │ │ │Vegetables│ │ │ │ │Vegetables ─────────────────┼──────┼───────┼──────────┼─────┼──────┼───────┼─────┼────────── Malnutrition │ .1│ 1.6│ .6│ 2.2│ .05│ .4│ .1│ Food Poisoning │ .3│ │ │ 2.5│ .05│ .2│ .08│ Acute Gastritis │ 3.2│ 6.3│ 9.3│ 3.1│ .9│ 2.│ 1.3│ 13.5 Acute Duodenitis │ .5│ .3│ │ .5│ .1│ 1.4│ 1.2│ 5.4 Acute Enteritis │ 2.5│ 3.4│ 3.│ 3.1│ 7.│ 1.│ 8.│ 5.4 Acute │ 26.3│ 53.2│ 19.9│ 29.2│ 25.3│ 38.6│ 35.6│ 64.8 Gastroenteritis│ │ │ │ │ │ │ │ Chronic Gastritis│ 1.1│ 6.│ 2.│ .8│ .2│ 1.4│ .3│ 5.4 Chronic Enteritis│ 2.│ 5.6│ 3.│ 2.2│ 1.1│ 3.3│ 1.3│ 13.5 Colitis │ 1.9│ │ │ │ │ │ │ Acute │ .1│ 2.2│ 1.│ 3.1│ .4│ .6│ .08│ Pancreatitis │ │ │ │ │ │ │ │ Chronic │ .5│ 1.7│ │ │ .2│ 1.2│ .5│ Pancreatitis │ │ │ │ │ │ │ │ Acute Liver │ .8│ 1.3│ .3│ 1.4│ 4.2│ 2.8│ 2.5│ 2.7 Disease │ │ │ │ │ │ │ │ Chronic Liver │ 3.│ 6.3│ 3.3│ 6.│ 1.1│ 2.5│ 1.6│ 13.5 Disease │ │ │ │ │ │ │ │ Acute Nephritis │ 9.1│ 12.2│ 12.7│ 12.4│ 5.1│ 6.7│ 4.1│ 8.1 Chronic Nephritis│ 4.5│ 11.6│ 6.7│ 7.8│ 2.9│ 6.7│ 2.1│ 13.5 Myocardial │ .1│ .34│ │ 1.1│ .3│ 2.│ .4│ 8.1 Degeneration │ │ │ │ │ │ │ │ Arterial Disease │ .1│ 3.1│ .3│ 2.2│ .3│ 3.1│ .66│ 1.8 Anemia pernicious│ .3│ .32│ │ │ │ │ │ Anemia secondary │ 4.2│ .32│ 1.2│ 1.5│ 1.1│ 2.5│ 1.5│ Thyroid Disease │ │ 7.5│ .3│ .7│ .3│ .2│ .3│ Adrenal Disease │ 1.6│ 1.3│ .3│ 1.5│ │ │ .08│ Diabetes │ │ .2│ │ │ │ │ │ Osteomalacia │ 5.2│ .4│ 2.3│ .2│ .1│ .6│ 2.8│ Osteitis │ .6│ │ │ │ │ │ │ deformans │ │ │ │ │ │ │ │ Arthritis │ │ .3│ .3│ 2.2│ │ .2│ .08│ Rickets │ .1│ 2.6│ .6│ .7│ │ │ .08│ Gout │ │ │ │ │ │ .4│ .08│ Sore Eyes │ │ .3│ │ .2│ .1│ │ .3│ Malignancy │ .05│ .9│ .6│ │ .05│ │ .6│ Tuberculosis │ 32.6│ 3.5│ 4.5│ 9.6│ 12.│ 1.7│ 17.2│ 5.7 ─────────────────┴──────┴───────┴──────────┴─────┴──────┴───────┴─────┴──────────