2 FOREWORD 
that strictly natural to them, yet they have not been influ- 
enced by any of the artificial procedures of the laboratory 
which are usually followed in investigations on animals. 
Though the object of the work was the pursuit of knowl- 
edge for its own sake, yet results of practical value have 
followed: hygiene has been improved; disinfection has 
been made scientific ; epidemics have been arrested ; some 
diseases, notably tuberculosis in monkeys, and spiro- 
pteriasis in parrots, have been practically eliminated. 
The value of the work is recognized by the keepers. 
Their interest has increased and their morale has 
improved. The frequent deaths in a large collection of 
animals are discouraging, and a good animal man must 
have courage and optimism — traits that are stimu- 
lated by the knowledge that every animal that dies is 
studied to determine the cause of death, and to prevent 
its recurrence. 
Some results of this study are to be considered as 
*'raw material," while others peimit cautious or tentative 
conclusions. The first include — visceral weights, inci- 
dence of certain lesions like anemia and hepatic cirrhoses, 
occurrence of calculi and observations on weak hind 
quarters, convulsions and constitutional diseases. The 
second include — eradication of tuberculosis and spiro- 
pteriasis, the response of the mammalian and avian heart 
to strain and disease viruses, the origin of pneumonia in 
birds, the genesis of bronchiectasis, the nature of osseous 
degeneration with relation to diet and alimentary tract, 
the comparative anatomy, physiology and pathology of 
the female genitalia, the occurrence of lesions in the 
thyroid comparable to those in man, the character of 
kangaroo disease. 
Great praise is due Dr. Herbert Fox and his assist- 
ants Drs. F. D. Weidman and E. P. Corson- White, for 
the splendid scientific spirit and thoroughness with which 
they have done this work, with no adequate remuneration. 
