20 DISEASE IN WILD MAMMALS AND BIRDS 
A direct and practicable application of these data will 
be in the direction of explaining some of the pathological 
states in domestic animals and man. There are indeed 
many disease entities or syndromes in these groups for 
which no useful hypothesis has been advanced, while for 
others a partial explanation has been offered, usually, 
however, inadequate wherewith to form the basis of 
rational prevention or therapy. Thus, for example, 
essential emphysema seems to be limited to the animals 
of civilization ; on the other hand, the anatomical basis of 
exophthalmic goitre may be seen throughout nearly the 
whole animal kingdom yet the clinical phenomena belong 
characteristically to man, and are occasionally seen 
atypically in the dog. While it may be impossible to 
give a complete comparative anatomy and physiology for 
each of the pathological states, the attempt will be 
made to treat all subjects analogically through the zoo- 
logical orders. 
The experimental pathologist may find the records of 
the Garden useful in his work. For example, he can know 
that rodents are not prominent among the orders shomng 
spontaneous arteriosclerosis, but that nephritis occurs 
among them in about a quarter of natural deaths ; or he 
may learn that the Primates have a good cardiac 
reserve while the Marsupialia have not. Too often 
experimental work is not based upon facts including 
natural probabilities. 
A collection of pathological data such as is presented 
in the following pages may be of assistance to vet- 
erinarians and managers of zoological gardens in the 
diagnosis of sickness in animals, both wild and domesti- 
cated. We do not presume to offer a system of veterinary 
medicine, but it is possible to introduce certain objective 
findings of practical hygienic and therapeutic value. Such 
observations are, however, limited and in our experience 
at the Philadelphia Garden the diagnosis of disease in a 
wild animal, excepting of course those which are per- 
