Part 41

Overeating is a factor that must be borne in mind when considering the hay- and grass-eating herbivora. Packing of the rumen is a not infrequent discovery. This condition is also found in certain seed- eating birds. As a supply of food is constantly at the disposal of these animals and exercise is prevented by captivity, continuous eating becomes their principal diversion. In this group also food poisoning was highest, a condition which may be due to (1) spoiled food, (2) poisonous substances in the foods, (3) fermentation of grass foods (spoiled hay or musty fodder). Malnutrition also, is higher than with any other diet, due probably to the somewhat meagre nutritious value of the food. This group also shows a high percentage of acute pancreatitis, degeneration of the liver, myocardium and arteries. Arthritis was present in this group 2.2 per cent., against 0.2 per cent. in all other groups.

A study of Table 19 demands a constant recollection of the morphology of the tract involved and its main points of vulnerability, the bacteria capable of living on the particular type of food or its constituents and the by-products produced during the digestion and absorption of these foods. Not one of these factors can be ignored in evaluating the influence of diet, which to be correct must supply elements in proportions that are chemically available for body needs (for instance, Von Wendt[59] found that more iron was required if the diet was deficient in calcium). These proportions must be worked out by carefully combined chemical and biological experiments.

MALNUTRITION.

There was one omnivorous beast, a Hamadryas Baboon, which represented the only true case of starvation, probably induced by nostalgia, as it never ate after coming into the Garden. Thirty cases of partial starvation or malnutrition are listed in our records, the majority among the rarer specimens, ten carnivorous, seven herbivorous and one omnivorous mammals, ten carnivorous and two seed-eating birds, due possibly to inappropriate diet or to some unknown factor that rendered the diet inadequate. At the autopsy nothing was found to account for death except the draining of all storage supplies.

STARVATION.

The reports of studies conducted during long laboratory fasts have been among the most valuable records for the understanding of the chemical requirements of diet and of the close chemical interrelationship existing between the different food factors. In absolute starvation life is very short, primarily because water is necessary for respiration, for dissolving products of metabolism and for preventing changes in digestive intestinal secretions. The amount of water needed varies with different species of animals. If the water is supplied, the organism is enabled to maintain its energy for continued existence from the destruction of its own tissues. The length of life depends upon the amount of protein ingested before the fast commenced, and the amount of stored fat and glycogen, especially that stored in the liver. The mechanism of the results is similar. The animal body uses first its available glucose, and when this is partially exhausted burns its stored fat and protein. The fat combustion is usually defective, ketone bodies appearing in the urine in large quantities. The change from fat to protein metabolism accounts for the premortal rise in metabolism which occurs usually a few days before death. The chemical composition and corpuscular richness of the blood is tenaciously preserved; glucose and protein concentration are practically normal up to the day of death. There is at times a slight increase in globulins and always an increase in fat due to its transportation from storage depots. The cause of death is primarily due to loss of substance in organs necessary to life and to an acid intoxication.

Wasting occurs first in stored substances, fat, glycogen, etc., then in the least used organs. The bones usually show some rarefication. The animal, as a rule, dies from acid intoxication before atrophy of the organs is marked.

In the wild, when animals are forced to seek their food with the expenditure of much energy and where feasts are often followed by fasts, this using up of storage supplies cannot help being a factor in preserving the integrity of the storage and eliminative organs. In captivity this cannot occur. Food is supplied regularly, exercise is lacking, consequently overloading and disease of storage and eliminative organs is more or less constant—a situation very marked in the Carnivora.

TABLE 20. _Detailed Analysis of the Various Diets Used at the Philadelphia Garden on Basis of 100 Grams of Mixed Food._ ═════════════╤══════════════╤═════════════╤══════════════╤═════════════ │ Omnivora │ Carnivora │ Herbivora │ Herbivora │ │ │ Succulent │ Coarse Food │ │ │ Vegetables │ ─────────────┼───────┬──────┼──────┬──────┼───────┬──────┼──────┬────── „ │Mammals│Birds │ Meat │ Fish │Mammals│Birds │ Hay │ Seed │ │ │ │ │ │ │ Food │ Food ─────────────┼───────┼──────┼──────┼──────┼───────┼──────┼──────┼────── Protein │ 14.3│ 11.5│ 15.6│ 17.2│ 6.1│ 3.2│ 6.4│ 7.1 Fat │ 9.5│ 7.2│ 18.8│ .3│ 2.6│ .5│ 2.2│ 1.3 Carbohydrate │ 26.7│ 41.2│ │ │ 18.5│ 25.7│ 35.9│ 51.2 Calcium │ .034│ .068│ .058│ .109│ .067│ .025│ .071│ .044 Magnesium │ .058│ .093│ .118│ .133│ .164│ .119│ .289│ .16 Potassium │ .497│ .713│ 1.694│ 1.671│ .538│ .242│ .644│ .324 Sodium │ .103│ .284│ .421│ .373│ .08│ .291│ .089│ .261 Phosphorus │ .263│ .484│ 1.078│ 1.148│ .556│ .342│ .692│ .458 Chlorine │ .117│ .377│ .378│ .528│ .038│ .044│ .073│ .063 Sulphur │ .338│ .486│ 1.146│ 1.119│ .134│ .125│ .217│ .163 Iron │ .0032│ .0063│ .015│ .0055│ .0018│ .0012│ .0022│ .0012 ─────────────┴───────┴──────┴──────┴──────┴───────┴──────┴──────┴──────

A further study of Table 19 in the light of the finer analysis of the ingredients of the diets, shown in Table 20, explains, at least in part, the high percentage of certain types of disease in relation to particular diets.

In the food of the first group, the omnivorous mammals, there is a moderately increased carbohydrate content and an unevenly balanced inorganic content, the last being the factor most at fault. The calcium and phosphorus are both so low that at the best the animal could only be in equilibrium, while any drain of the fixed bases would sooner or later have to be replenished from the calcium and phosphorus storage depots, the bones. Osteomalacia is most marked in the Cebidæ, monkeys whose diet is even lower in these same elements: calcium .025, phosphorus .116, and iron .0008 per 100 grams of food. The inorganic composition of all animals is grossly similar; the typical digestion developed from the habitual diet of the animal explains the more apparent changes and variations in their reactions to certain deprivations.

IRREGULARITIES OF INORGANIC METABOLISM.

Twelve essential elements are present in the body, namely: carbon, nitrogen, hydrogen, oxygen, phosphorus, calcium, sulphur, sodium, chlorine, potassium, iron, magnesium. Of these, five are furnished by the protein molecule and three of the five are duplicated in the fats and carbohydrates; the remaining seven must be present in the mineral ash. These elements functionate in three ways, (1) as constituents of bone, (2) as essential elements of organic compounds, (3) as soluble salts in body fluids. Chlorine, sodium, sulphur are supplied in sufficient quantity with most diets. In the case of chlorine, marked differences exist between the herbivores and carnivores. The meat-eating mammals easily acquire sufficient sodium chloride from the flesh and blood of their victims, while the herbivores on the other hand, find in their vegetable food large amounts of potassium and very little sodium or chlorine which must therefore be acquired separately. Both omnivores and herbivores crave salt, probably because this large potassium content of vegetable food tends to increase the sodium elimination. A deprivation of salt always leads to a distaste for foods rich in potassium. So far as is known excessive sodium stimulates protein catabolism, and through the overstimulation of the digestive tract, may interfere with the absorption of food.

Sulphur is largely taken into the body in organic combination with the protein, (a very little inorganic sulphur appears in the drinking water) therefore if the protein requirements are adequate the sulphur will usually be adequate.

Magnesium is abundant in meat and most plant tissues; so that except in diets of highly refined foods, it is more often excessive than deficient.

The other elements, calcium, phosphorus and iron are frequently insufficient, especially for animals on omnivorous diet (cf. Table 20). Phosphorus enters into every living cell, and in cases of starvation is excreted up to the last. It is involved in practically all the cell functions. In the body it is present (1) as an inorganic compound in the bone tissues and blood where it helps to maintain neutrality, (2) as phosphorus-containing protein, phosphatids and phosphoric esters of a carbohydrate, all closely associated with the cell and its nucleus. In foods, phosphorus occurs in the same positions, that is, inorganically or combined with protein, fat or carbohydrate. It is not entirely proved but is very probable that the phosphorus in organic combination has the greater metabolic value, inasmuch as there is greater storage of nitrogen and stimulation of tissue growth on foods containing phosphorized proteins, fats, etc. It has been shown, however, that the animal body can satisfactorily supply its phosphorus requirements by inorganic phosphates. The omnivorous diet, even the widely varied diet of man, is very often deficient in phosphorus, a fact which becomes very important when we consider that the omnivorous diet produces many acid residues which must be neutralized, and that phosphorus is largely responsible for the maintenance of tissue neutrality. Voit showed that the phosphates excreted during starvation were withdrawn from the bones; and there is much proof that during the daily metabolism a certain slight movement of phosphorus takes place. The metabolized phosphorus is excreted by carnivores practically from the kidney alone; by herbivores almost entirely through the intestinal wall, while in the omnivores it is excreted by kidney and intestinal tract. Whether these facts have any real influence on the phosphorus need of different types is not altogether determined.

Calcium also enters into many of the essential functions of life, coagulation of the blood, contractility of the heart, etc. Omnivorous diet is usually deficient in this element, which is very irregularly distributed both in animal bodies and plants. Insufficient amounts lead to deprivation of body tissues and to the production of osteomalacia- like conditions. Voit produced marked thinning of the skull bones and sternum by a diet poor in calcium. Steenbok and his associates had the same results in cattle by feeding “shorts” a diet rich in magnesium. Etienne[60] showed that an excess of magnesium in an otherwise well balanced food caused a continual loss of calcium. Adults stand a deprivation of calcium much better than children or young animals. They often show no symptoms and retain a normal blood content as the losses from the blood and soft tissues are promptly replaced from the bones. Sooner or later all these animals show weakness and flexibility of the bones. Osteomalacia occurred in 5.2 per cent. of the animals on an omnivorous diet, that is this number showed gross evidence of absorption of bone salts. This condition occurring in man and the lower animals is a generalized softening of adult bones that were at one time normally calcified. Three clinical varieties are recognized in man: a mild form seen in pregnant, puerperal and lactating women, a senile form in which the lesions are usually limited to the pelvis, and a severe progressive form encountered in both sexes and at any age. This last form ends in marasmus. Its chemical characteristic is a loss of calcium and phosphorus with retention of sulphur and magnesium.

The progressive type has occurred very frequently among the Cebidæ whose diet on careful examination, showed a protein content low in quantity, poor in quality, and especially deficient in the phosphorus-containing proteins and total fat. The carbohydrate was high. The ash was small in amount and predominatingly acid. The daily ration often showed only an unweighable trace of calcium, phosphorus or iron. Sodium, potassium, sulphur and magnesium, on the contrary, were present in amounts sufficient for equilibrium or in excess. The Vitamines A.B.C. were present but were not always correctly proportioned. The fat soluble A was low and in some daily rations was entirely lacking.

Diet has at various times been proposed as at least one factor in the production of this condition, a premise that has gained considerable weight through the increase in the number of cases, both in man and in the domesticated animals, reported from the war-famine district of Central Europe where the dietary was restricted and unbalanced. It has been shown that when calcium is low in the diet, the amount excreted materially exceeds the intake. Benedict[61] has further shown that even during absolute fasts calcium is excreted. The requirements of this element for man have been fairly well worked out, but for animals we have no standards. Still it seems certain from the foregoing observations that storage supplies are called upon very early in cases of deprivation, while in pregnancy and lactation when the calcium requirements are greatly increased, a reason is found for a higher incidence of osteomalacia, Steenbok and Hart[62] have shown that the skeletons of cows and goats gave evidence of a drain of inorganic salts during the production of milk unless the calcium and phosphorus of the diet were liberally supplied. In osteomalacia it would seem that inefficient diet, if not the cause, was at least a very potent factor in pathogenesis. The disturbance of the calcium-phosphorus-metabolism may be due to the deprivation of the alkaline salts as in the famine osteomalacia, to a drain from the alkaline storage of the body associated with an inefficient diet as in the osteomalacia of pregnancy and lactation or to the combined action of a diet faulty in more than its salt content, which by the production of acid in its oxidation and by favoring the development of acid-forming bacteria, causes a drain of the body alkali for neutralization of the acid; or it may possibly be due to a combination of all these factors acting through their influence on the ductless glands.

Paget’s disease or Osteitis Deformans is a chronic constitutional process which usually involves all the bones of the adult skeleton. DaCosta[63] believed it to be a disorder of bone metabolism probably dependent upon absence or perversion of some internal secretion. We have had the unique opportunity of observing three cases of this disease in Cebidæ, the family of monkeys which has presented the highest incidence of osteomalacia. The experience is all the more interesting because of the typical picture presented by the specimens, and of the absence of references in the literature on the subject, to the occurrence of the malady in wild animals. The interesting point about these cases lies in the fact that the disease appeared in all three only after lime water was added to the diet to supply the deficiency of calcium.

Search for literary record of the disease brought to light a case in a horse that Barthelemy[64] described, but this involved the epiphyses of the bone while osteitis deformans is confined as a rule to the diaphyses. This case was probably more closely allied to osteitis fibrosa cystica. Goldman[65] described examples in fowls and Rossweg[66] refers to specimens in domestic goats and monkeys. Many of these cases first come under observation through fractures, an accident common to osteomalacia, but very rare in well developed osteitis deformans. The diet of our monkeys was exceeding low in those substances essential to bone development. Sherman[67] has shown that the calcium balance is regulated to a certain extent by the calcium ingested, and that when the diet is poor in this element, the output materially exceeds the intake, a condition which is definitely changed when the animal is put on a diet high in calcium.

So far as we could find there are no recorded studies of the mineral metabolism of beginning cases of Paget’s disease. It seems possible from the study of osteomalacia that the low mineral and otherwise faulty diet, added to the symptoms produced by that diet might so disturb the chemical equilibrium, directly through the neurotrophic mechanism or through the perversion of the ductless glands, that the mere addition of the lime water might entirely change the pathological picture. This is in accord with the histology where the initial lesion is resorption of bone followed by irregular proliferation. It is also in accord with the probable chemistry of calcification. These animals all showed a lowered carbon-dioxide-carrying-power of the blood, and therefore lowered ability to carry calcium in solution. It is possible that Paget’s disease is but a stage in a deficiency disease, a faulty reparative response through a disordered neurotrophic mechanism, or through a perversion of the glands governing calcium metabolism. Such perversion could be caused by an improperly balanced diet, or by the addition of an excess of calcium to the diet of an animal whose body fluids were unable by reason of previous faulty diet or other disorder, to hold it in solution. In young animals the calcium demands are much higher than in adults, a need met in the high calcium content of breast milk, a content in excess of almost every other food, but apparently just sufficient to maintain calcium equilibrium. After it is weaned the young animal frequently shows disorders of its inorganic metabolism. Herter estimated that a child should store at least 0.1 gram of calcium daily and he described many cases of arrested bone development occurring during infancy and early childhood, because of an inefficient assimilation of calcium. One case, probably of this character, was found in a Hamadryas Baboon (_Papio hamadryas_) a typical example of infantilism. The animal was an adult male about half the size of an adult female. His skin was fine and more delicate than normal, the bones were small and slender, contour of body was that of a young animal, genitalia were imperfectly developed, thyroid gland apparently normal, gastrointestinal tract atrophic, associated was a slight arthritis, portal cirrhosis of liver and diffuse nephritis.

First among the results of inorganic insufficiency in youth stands Rickets. This disease occurs in children starting usually at about the sixth month and continuing with irregular remissions for several years. The bone changes, which are the most prominent, are always associated with more or less severe anemia, a general lowered resistance and flabby musculature. The excretion of calcium is very high in the feces and low in the urine. There is a frequent negative calcium balance dependent upon the great loss in the feces. Healing is preceded by a hyperretention of calcium and a relative increase in the urinary calcium. The excessive loss of calcium in the feces is not brought about through the agency of fats because fat could only remove calcium as insoluble soaps and these are not at all increased. This fact contradicts the idea of fat starvation as a cause of rickets. Howland and Kramer found that the blood in active rickets had a normal or slightly lowered calcium content, but a regularly reduced phosphorus content. The latter deficiency was extreme at times. They ascribe to this deficiency the failure of the bones to calcify. It can be readily understood that a decrease of phosphorus in the blood would render difficult the precipitation of calcium phosphate.

Recently two series of studies, the first by Pappenheimer, Zucher and McCann and the second by Shipley, McCollum, Park and Simonds have shown that rats fed on a diet low in calcium but with a sufficient amount of fat soluble vitamine and phosphorus develop a bone condition with many fundamental resemblances to rickets. They were also able to produce the condition with an excess of calcium and deficiency of phosphorus. On the first diet, the condition differs from rickets in that the arrangement of the proliferating zone of cartilage cells is maintained and the evidence of bone resorption in the diaphyses is excessive. A diet deficient in both calcium and phosphorus leads to an atypical rickets.

In the animals autopsied at this Garden rickets occurred very much more frequently in the flesh-eaters than in any of the other dietary groups. On closer analysis it was found that rickets in almost every case appeared in the carnivores which did not receive bones as a part of the food. Rickets occurred frequently in the omnivorous macaques which however did not show osteomalacia, although they belong to the same dietary group as the Cebidæ. The reason they did not suffer the latter disease while adult but had rachitic young is probably due to the fact that this monkey group, which breeds best in our Garden, receives in addition to the diet given to Cebidæ one raw egg. This increased the calcium content of their food more nearly to the requirements of these mammals. These monkeys also have mouth sacs, which enable them to acquire more food per kilo of body weight than the smaller Cebidæ which are not so advantageously equipped. The food even in the amounts consumed by the macaques is low in calcium, phosphorus and iron. It is very possible that there are enough of these ingredients present as a rule, to maintain the animal in organic equilibrium, during normal life, and possibly even enough to supply the needs of the embryo but not sufficient to maintain the young during the period of lactation. A few macaques dying during the delivery of young showed slight osteomalacic changes in the pelvis. This was notably present in one described in detail by E. A. Schumann.

The calcium requirements of the female are always much increased during pregnancy and lactation due to the withdrawal from the mother to meet the needs of the embryo and nursling. Forbes and Beegle[68] found that lactating animals made heavy drains on their storage calcium even when the diet was liberal and the animal was storing nitrogen.