The results of the experiments of this series likewise indicate that the Belgian hare is more resistant to caffein than the rabbits of other varieties. Thus, of the four gray rabbits (Nos. 235, 316, 395, and 396), which received 267 to 283 mg of caffein per kilo, two died and two lived,[B] one of which, 396, showed the presence of coccidiosis of the liver. On the other hand it will be observed that the black and white rabbits which received from 270 to 275 mg of caffein per kilo all died from the effects of the drug; one within 1 hour and 25 minutes and another within 50 hours after the administration of the caffein, while No. 340 died in the night. Furthermore it will be noted that of the last three rabbits of this series, which were Belgian hares and received 290, 293, and 300 mg of caffein, two died six hours after the injection, while the other, No. 397, lived three days. The minimum fatal dose of caffein for Belgian hares is, therefore, about 290 to 300 mg per kilo when injected subcutaneously, which is about 50 per cent greater than for rabbits of other varieties. [B] Survived first dose. SERIES E. It was shown in series A that 0.15 caffein per kilo caused symptoms of intoxication. Before concluding, however, that this is the smallest dose which causes symptoms of poisoning, a number of experiments were performed with smaller doses. It was found that in the great majority of cases 0.1 caffein per kilo may cause diuresis, but no nervous or muscular symptoms. In some rabbits, however, even such a dose proved fatal. Post-mortem examinations in these cases showed the presence of coccidiosis of the liver, and it will be recalled that similar observations were made before. It is quite possible, therefore, that coccidiosis of the liver is an important factor in decreasing the resistance to caffein. Experiment 551 (p. 25) shows that other conditions may likewise increase the toxicity of caffein. _Rabbit 325. White, female. Weight, 1,065 grams. Diet, oats._ March 17: 11 a. m., 6 cc 2 per cent (112 mg per kilo) caffein injected subcutaneously in the back. About 5 cc of urine squeezed out from bladder before injecting caffein. March 17: 1 p. m., hind legs crossed and stretched out, front legs also extended; rabbit lying stretched out on her belly. March 17: 5.40 p. m., rabbit still alive, condition somewhat improved. March 18: 9 a. m., found dead, stiff and cold. _Autopsy_: Hemorrhagic area at point of inoculation; subcutaneous region of both thighs presented a hemorrhagic infiltration of the tissues; liver contained lesions of coccidiosis; other organs apparently normal. _Rabbit 330. Belgian hare, female. Weight, 935 grams; poorly nourished._ March 18: 3.35 p. m., 5 cc 2 per cent caffein (107 mg per kilo) injected into subcutaneous tissues in the back; 5.30 p. m., no symptoms. March 19: 9 a. m., no symptoms. March 25: Weight, 825 grams. _Rabbit 329. Belgian hare, male. Weight, 775 grams; poorly nourished. Received March 18._