----+--------+-------+-------------+--------------+-------+------------ 325| 1,065 | 112 |2 hours |Less than | Oats |White female. | | | | 22 hours | | 330| 935 | 107 |None |Survived | |Gray. 329| 775 | 103 |do. | do. | |Gray male. 320| 1,040 | 115 |2 hours |46 hours | Oats |Black male. 551| 1,450 | 100 |30 minutes |Less than | do. |Gray female. | | | | 24 hours | | ----+--------+-------+-------------+--------------+-------+------------ ADMINISTRATION BY MOUTH. These experiments were carried out on two varieties of rabbits, the white and the gray. The diet consisted chiefly of oats, but in a few cases carrots formed the exclusive diet. Food and water were given ad libitum. A 2 per cent solution of caffein was administered through a stomach tube. Since the resistance to most drugs is commonly supposed to be greater when given by mouth than when administered by any other path, doses of 175 to 200 mg per kilo were fed in a series of preliminary experiments, all of which were performed on gray rabbits weighing from 865 to 1,135 grams, and which were fed carrots for several days previous to the experiment. Three of the rabbits survived, two without showing any symptoms; in the other case paralysis of the posterior extremities was observed five hours after he received caffein and he was found dead the next morning. Unfortunately no autopsy was performed. The low resistance to caffein of this animal was probably due to some abnormal condition which developed about the time of the experiment, since this rabbit received 325 mg of caffein per kilo two weeks previously and increased reflexes only were observed as a result of this treatment. Hence 200 mg of caffein per kilo can not be considered the toxic dose when fed by mouth. In the following experiments larger doses were therefore given. SERIES A. _Rabbit 248. Belgian hare. Weight, 1,170 grams. Diet, oats._ November 17: 1.20 p. m., 19.5 cc 2 per cent caffein (330 mg per kilo) administered by the mouth; 4.30 p. m., somewhat hypersensitive. November 19: No symptoms; at 9 a. m., urine collected, no reduction of Fehling's solution; rabbit survived. _Rabbit 241. White male. Weight, 1,380 grams. Diet, oats._ November 17: 1.15 p. m., 20 cc 2 per cent caffein (290 mg per kilo) administered by the mouth; 4.30 p. m., some hypersensitiveness, but no other symptoms. November 18: 9 a. m., urine collected, no reduction of Fehling's solution; no symptoms; rabbit survived. _Rabbit 249. Belgian hare. Weight, 890 grams. Diet, oats._ November 17: 1.30 p. m., 14.5 cc 2 per cent caffein (325 mg per kilo) administered; 4.30 p. m., hypersensitiveness; no other symptoms. November 18: 10 a. m., no symptoms; urine collected, no reduction; rabbit survived. SERIES B.