The diseases of this organ are known only by their physical effects, chiefly by causing physical or functional defects in other organs and to a minor degree by purely physiological irregularities in the heart itself (tachycardia, arrhythmia). All the latter and most of the former are subjects discovered by observation during life and unfortunately cannot be included in the study at hand. Both states are well known to the veterinarian who diagnoses them with reasonable ease in animals that can be handled; I saw one case of arrhythmia in a monkey for which no adequate gross morbid explanation was found postmortem. Some of these functional abnormalities are certainly caused by myocardial disease and cardiac failure has occurred among many orders. An interesting observation was made by Plimmer[6] on several large birds (ostriches, storks, cassowaries) which apparently died from this condition; at autopsy he found myocardial degeneration, or epicardial edema or only a flabby heart. Lack of exercise was held responsible by this observer. Such cardiac deaths have probably been encountered at this Garden but we have accounted them to shock, or gastrointestinal disease; this matter will be discussed on a later page. CORONARY ARTERY DISEASE. If a degenerative sclerosis of coronary vessels be the cause of angina pectoris then perhaps paroxysms of this kind occur, for we have seen such anatomical changes in the heart of three widely separated varieties of animals, a Nylghaie, a Hamadryas Baboon, a Macaque, and a Brown Pelican. The history of these animals does not register anything resembling the clinical picture of angina pectoris in man, and they did not come to their death from the arterial changes in the heart alone since sufficient other pathology also existed. KINDS OF PATHOLOGICAL CHANGE.