Pathology may be difficult upon an anatomical basis, but when we engage to explain functional physiological defects we are surely embarked, with a poor compass and weak rudder, upon an uncharted sea. One knows, of course, that all animals require the same amount of food elements per kilo of body weight, that man eliminates his nitrogen as urea and uric acid, that monkeys do the same, that most other mammals destroy uric acid and excrete allantoin, that birds and reptiles form uric acid but chiefly urates, that there is an adaptation of alimentary tract and diet, that herbivores have a high threshold for carbohydrates, that there is a variable quantity of enzyme present in different organs and in different animals, that vitamins, whatever they may be, are necessary for the growth of young animals, that hormones exist whereby correlations of parts are kept normal—but these things, rather than being learned thoroughly from animals, have merely been substantiated by comparisons with man. Constitutional diseases so-called, from which the necessity to investigate much of this physiology originated, are little known in the wild animal. Many cases of so-called gout have been encountered and we have seen an instance of diabetes in a fox, but more extensive experience is needed for definite practical comparisons. This applies to thyroid and pituitary disorders and to the vague conditions we have at times been obliged to call marasmus or inanition. Some attention has been given to the study of diets for the wild specimens of our Garden, but no systematic observations have been made or records kept upon purely physiological subjects. Reference will be made at appropriate places to accepted comparative physiological facts, but our statistics permit additions to such knowledge only in a limited manner and in isolated instances. Doctor Corson-White has very ably summarized the diet, alimentary tract and physiology of the zoological groups with the pathology as found in our records. A word might be added here as to the destruction of animals by injury from fighting and harassment by others in the cage. Fighting doubtless causes death, especially when males are together, but it is our experience that in cases of traumatic death search should always be made to see if the resistance of the dead animal had not been reduced by some disease. This is well illustrated in birds. Very frequently a specimen will come to autopsy with its head feathers plucked out, or with a billthrust in the wing or pelvic region. Such birds are not infrequently suffering from malaria, or heavy intestinal parasitism or from organic disease whereby the resistance and self-preservatory power has been decreased.