Thrombosis is practically always a parasitic or an infectious process although at times considerable difficulty is encountered in explaining the source of the worms or bacteria. Thus, for example, the iliac or femoral thromboses which are at the bottom of intermittent claudication, are frequently quite vague in origin. We have had one such case in a deer in which a partly occluding thrombangeitis existed in both femoral arteries and veins. Mesenteric thrombosis, a serious condition in cattle and horses from infestation with sclerostomum or strongylus, has not been proven at the Garden, but we have seen one case of numerous thromboses of the venous radicals in the jejunal wall apparently due to some nematode larvæ; the specimens were so soft by decomposition that determination was not attempted. There occurred a thrombosis of the cava and aorta originating from a necrotizing cloacitis, apparently streptococcal in nature, in a Demoiselle crane. The clot, while not totally occlusive, extended nearly as far as the heart in the vein and the abdominal aorta. There is also on record a thrombosis of the vena cava and right pulmonary vein in an American beaver, harboring Hepaticola hepatica in the liver, with a fibrosing pneumonia due to this parasite. Another case in which parasites seemed to take a hand concerned a common raccoon with tapeworms (sp.?) in the small intestine and microscopically discoverable parasitic parts in the lungs; these organs were the seat of extensive congestion and venous thrombosis, the latter containing really enormous numbers of diplococci. The parasites probably paved the way for bacterial invasion. A frank case of septic thrombotic aortitis was noted in a Rice Grackle, the infectious focus apparently being a vegetative “tricuspid” valvulitis. ARTERITIS.