Age is likewise a factor in the toxicity of caffein, young animals being more resistant than the full-grown and older animals; this was shown in experiments on rabbits, cats, and dogs. The symptoms of caffein poisoning also were different in puppies and in full-grown dogs. Different diets, such as carrots and oats, did not influence the resistance of rabbits and guinea pigs to caffein. Low protein diet tends to decrease resistance to caffein in dogs. Young growing dogs are less resistant to caffein on a meat than on a milk diet. Caffein is not cumulative in the rabbit or dog, even if administered for a considerable length of time. Some degree of tolerance may be induced in the rabbit under certain conditions, but not in dogs under the conditions of the experiments made in this investigation. The possibility, however, that dogs may acquire tolerance for caffein is not excluded. Although the rabbit tolerates a much larger single dose of caffein than the dog, it was found, in experiments on chronic intoxication that the rabbit is less resistant to caffein than the dog. The toxicity of caffein is probably increased under pathological conditions, since comparatively smaller doses were fatal to rabbits, cats, and dogs, when marked lesions not due to caffein were found at autopsy. Glycosuria was observed in rabbits, guinea pigs, and cats when caffein was given in sufficient amounts. TABLE 18.--_Acute caffein intoxication: Table showing average minimum toxic and minimum fatal doses for adult animals._ Table headings: SC: Subcutaneously. BM: By mouth. IP: Intraperitoneally. IM: Intramuscular. IV: Intravenous.