October 20: 13 cc of 2 per cent caffein (0.236 gram per kilo). About 15 minutes later cat became irritable, reflexes increased, persistent crying, stiffness of extremities, diarrhea present; 4.30 p. m., stiffness of muscles, coordination much disturbed, walked with great difficulty; 4.30 p. m., no new symptoms, persistent crying continued. October 21: Found dead. _Cat 20. White kitten. Weight, 790 grams._ October 20: 11.35 a. m., 10 cc 2 per cent caffein (0.25 gram per kilo) given subcutaneously; 12 noon, convulsions followed by paralysis; 1.30 p. m., still breathing, apparently in comatose condition, lay on its side, dyspnoea, profuse salivation; 4 p. m., convulsions and death. The results of the experiments of series B show that a dose of even 0.2 caffein per kilo is very toxic for the cat. Symptoms appeared in one animal 40 minutes after the injection of caffein. Some of them were found dead 18 hours after injection, which means that the duration of life was probably a great deal less since there was evidence that they had been dead for some time. Death occurred quite soon after larger doses were injected. Cat No. 3 died 30 minutes after it received caffein. The amounts employed in these experiments can not be considered therefore as the minimum fatal doses. Smaller doses were then tried, as shown in the experiments of the next series. SERIES C. Experiments were performed on five cats which received from 140 to 155 mg per kilo, as follows: _Cat 24. Striped. Weight, 1,300 grams._ October 25: 10 a. m., 50 cc urine, albumin moderate amount--no sugar; 10 cc caffein injected subcutaneously at 12 noon; 12.30, irritable, cried persistently, no appetite; 4 p. m., no convulsions, but persistent crying. October 27: Cat was still alive. _Cat 17. Weight, 2,620 grams._ October 12: 9.30 a. m., 65 cc urine collected; more than a trace of albumin present, no reduction of Fehling's solution; 3 p. m., 20 cc 2 per cent caffein (150 mg per kilo) injected subcutaneously; 3.15 p. m., irritable and restless. October 13: 9 a. m., about 15 cc urine collected, reduction of Fehling's solution marked; osazone test also positive. _Cat 23. Black and white. Weight, 1,645 grams._ October 25: 10 a. m., 140 cc urine collected (since October 23), small amount of albumin present, no sugar. October 27: 9 a. m., no albumin; no sugar in urine; 11.50 a. m., 12.5 cc caffein injected subcutaneously (0.15 gram per kilo); 1 p. m., convulsions and death. _Cat 7. Striped kitten. Weight, 1,285 grams._ October 11: Urine collected, no albumin, no sugar; 9.50 a. m., 10 cc 2 per cent caffein injected subcutaneously in the back; 10.10, violent convulsions lasting about 30 seconds; 10.20, convulsions of shorter duration; 10.30 convulsions; 10.35, convulsions lasting a few seconds; urine passed about 10.20, contained a moderate amount of albumin, but there was no reduction of Fehling's solution; 10.45, profuse salivation and paralysis; died about 10.50.