-----------+--------+----------- Date. | Weight.|Treatment. -----------+--------+----------- |_Grams._| _cc._ Aug. 20 | 2,030 | 20.0 Aug. 21 | 1,950 | 19.5 Aug. 22(1)| | Aug. 23 | 1,955 | 19.5 Aug. 24 | 1,905 | 19.0 Aug. 25 | 1,890 | 19.0 Aug. 26 | 1,780 | 18.0 Aug. 27 | 1,765 | 17.5 Aug. 28(1)| | Aug. 29 | 1,630 | 16.5 Aug. 30 | 1,540 | 15.5 Aug. 31 | 1,510 | 15.0 Sept. 1 | 1,425 | 14.0 -----------+--------+----------- (1) Not fed. September 2, found dead 9 a. m. _Autopsy_: The lungs were badly congested, the posterior lobe of the right lung showing hepatization; the liver was considerably enlarged and congested; the mucous membrane of the stomach and small intestines was congested and showed numerous hemorrhagic spots; the kidneys showed slight congestion; all other organs normal. SERIES D. The evidence brought forth in the preceding pages regarding cumulation of caffein naturally suggests the question whether or not the body acquires a tolerance for it. This question has already been answered in the affirmative by Gourewitch,(28) but owing to the method he used for the identification of caffein and the few experiments made his results are not conclusive. The experiments of series A, B, and C might be regarded as indicating that tolerance for caffein is not acquired by the rabbit. It was noticed, however, that the rabbit apparently does tolerate increasingly larger doses under certain conditions, as the following experiments show: _Rabbit 223._ _Belgian hare, male._ October 22: Weight, 1,520 grams; 15 cc 2 per cent caffein injected subcutaneously at 2 p. m. November 1: 10.30 a. m., weight, 1,510 grams; 17 cc 2 per cent caffein injected subcutaneously (225 mg per kilo), reflexes observed, but no tetanus. November 4: 10.30 a. m., weight 1,535 grams; 19 cc 2 per cent caffein injected subcutaneously at 2.40 p. m.; 4.40 p. m., no symptoms. November 8: Weight, 1,425 grams; 20 cc 2 per cent caffein (285 mg per kilo) injected at 11.45 p. m.; 5 p. m., no symptoms. November 17: Weight, 1,325 grams; 22 cc 2 per cent caffein injected at 2.55 p. m. (329 mg per kilo), no symptoms. November 18: Rabbit in good condition. _Rabbit 224. Belgian hare, female. Diet, carrots._ October 18: Weight, 1,935 grams; 11.20 a. m., 15 cc 2 per cent caffein (155 mg per kilo) injected. November 1: Weight, 1,780 grams; 20 cc 2 per cent caffein (224 mg per kilo) injected subcutaneously, reflexes increased, muscle tremors present, but no other symptoms. November 4: Weight, 1,710 grams; 21.5 cc 2 per cent caffein (252 mg per kilo) injected. November 8: Weight, 1,435 grams; 22.5 cc 2 per cent caffein or 314 mg per kilo injected at 11.40 p. m.; 5 a. m., no symptoms. November 17: Weight, 1,340 grams; 24 cc 2 per cent caffein (358 mg per kilo) injected subcutaneously. November 18: 9 a. m., rabbit died.