21. The incidence of tumors 464 22. An analysis of the breeding, captivity and visceral distribution of neoplasms, of tumor-bearing animals 466 23. An analysis of the incidence, character and distribution of tuberculosis 486 24. The incidence of parasites in the zoological orders 630 25. The incidence of heterakis in pheasants 635 26. The incidence of various parasitic orders and families 636 27. The visceral distribution of parasites 639 28. The occurrence of blood parasites in zoological classes 651 FOREWORD BY CHARLES B. PENROSE The work on which this book is based was begun in November, 1901. From that date, systematic autopsies were made on animals dying in the Philadelphia Zoological Garden. Previously autopsies had been made very rarely and only on animals of especial importance and interest. Pathological conditions were occasionally noted in animals subjected to anatomical study. The work was strictly volunteer, for there was no one on whom the Society had the right to call. Dr. Henry C. Chapman, a former Director, whose interest was in physiology and comparative anatomy, made nearly all the autopsies that were made before the beginning of the present work. In the annual reports from the foundation of the Garden in 1872, very few such examinations are recorded. In some reports there are lists of important deaths, but no record of the cause of death. This state of things was not peculiar to the Philadelphia Garden. It existed in every zoological garden in the world. It exists in most of them to-day. When an animal died it had no interest or value except for its hide and bones. Rare specimens were sent to the Academy of Natural Sciences from the Philadelphia Garden. The great majority, however, were immediately destroyed, and thus during the twenty-nine years from the foundation of the Garden, preceding this work, there have been lost many opportunities—some of which will never recur—of increasing our knowledge of pathology. This book gives results of the study of animals that have not been subjected to experimental procedures and conditions, and though their mode of life has not been that strictly natural to them, yet they have not been influenced 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 knowledge 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 spiropteriasis in parrots, have been practically eliminated.