The purpose of a menagerie under the auspices of a zoological society can scarcely be put into better words than those found in this quotation from Sir Francis Bacon’s _New Atlantis_. Apt as this description of the mythical island’s collection may be, it is but a reflection of the teachings of Plato’s original legend of a perfected community, and the practical applications of these teachings by Aristotle in his _Anatomy and Physiology of Animals_. The history of human study shows a constant investigation of lower forms of life, ever broadening in its scope, ever more satisfying in its explanation of biologic problems and ever increasing in value from an economic standpoint. If, however, all animals are to be subjected to “dissections and trials” there inevitably will come under observation many specimens presenting variations from the accepted mean or standard or even from an average for their kind and therefore approaching what may be called pathological. The desire to explain the abnormal has had the effect, during the half century since Virchow defined cellular pathology and Darwin systematized the world’s knowledge of comparative biology, of directing attention to comparative pathology and of stimulating the study of veterinary medicine. Moreover in the past twenty-five years much work has been done and many isolated publications have appeared upon the diseases of wild animals, notably Bland-Sutton’s work, _Evolution and Disease_ (1895), a thoroughly scientific and most charmingly written book, but rather elementary in its approach of the subject of pathology, and Wood Hutchinson’s _Diseases of Animals_, a more or less popularly presented treatise. I am unaware, however, of any systematic monograph upon the subject wherein we may find data showing the character of pathology in the various animal groups or the incidence of the various lesions. The reports of some zoological gardens contain the result of medical and pathological data collected for the report period. The publication of greatest merit and value is that from the Zoological Society of London, whose huge collection studied by a large official personnel makes it possible to present valuable data. The New York Zoological Park uses its material in a similar manner and has been able to explain some of the knotty problems so frequently met in wild animal collections.