Changes in the Character and Location of Arterial Lesions in Mammals and Birds in the Philadelphia Zoological Garden

Improved nutrition for mammals and birds at the Philadelphia Zoological Garden has been followed by continued increases in the frequency of arteriosclerosis and by changes in the character and location of the lesions. During the first decade after diets were improved the large atheromata of the proximal aorta and brachiocephalic arteries of birds were replaced by smaller, more compact lesions, usually of the abdominal aorta. At the same time many species of mammals developed atheromata of the aorta, whereas earlier these lesions had been found chiefly in baboons and monkeys (Cercopithecidae). During the second decade of adequate nutrition, and especially since 1950, arteriosclerosis of the coronary arteries has become relatively common in both mammals and birds. Usually this lesion has developed in the distal, intramural segments of the coronary arteries, as intimal thickening and occlusion. Most frequently it has been associated with myocardial fibrosis, but it also has led to myocardial infarction and sudden death in both mammals and birds. Present evidence suggests that this lesion reflects a response of adequately nourished animals to population densities.