INTRODUCTION 39 
vidual immunity and whole groups are apt to be carried 
off. Occasionally hygienic measures stay the ravages, at 
other times nothing seems to avail. Fortunately it is 
sometimes possible to sacrifice infective specimens and 
remove contagion. We have had few serious outbreaks, 
unless one might call our former heavy infection with 
tuberculosis in monkeys an epizootic. The principal ones 
were an unexplained water fowl disease which carried 
off one hundred and forty-six birds, an imported epi- 
zootic of quail disease which killed about the same 
number, a few cases of blackhead among wild turkeys, 
and a small group of cases of amcebic dysentery in 
monkeys and of thrush in passerine birds, and a small 
number of tuberculous pneumonias in snakes. 
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 ani- 
mals, 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 ani- 
mals, have merely been substantiated by comparisons 
\\dth man. Constitutional diseases so-called, from which 
the necessity to investigate much of this physiology origi- 
nated, 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 
