_Rabbit 217. White. Weight, 1,355 grams. Diet, oats._ October 29: 10 cc 2 per cent caffein (147 mg per kilo) injected subcutaneously at 1.51 p. m. 5.15 p. m., rabbit alive; survived. _Rabbit 219. Maltese. Weight, 1,820 grams. Diet, oats._ October 29: 14 cc 2 per cent caffein injected subcutaneously at 1.40 p. m. (153 mg per kilo); 5.15, rabbit alive; survived. _Rabbit 194. White female. Weight, 1,490 grams. Diet, oats._ October 14: 13 cc 2 per cent caffein (174 mg per kilo) injected subcutaneously; increased reflexes and tremors were observed. October 15: Condition of rabbit good; no symptoms. _Rabbit 191. Brown male. Weight, 1,915 grams. Diet, oats._ October 14: 16 cc 2 per cent caffein (167 mg per kilo) injected subcutaneously; reflexes increased and tremors present. October 15: Condition of rabbit good. A study of this series shows that about 150 mg of caffein per kilo caused increased reflexes within one to two hours after injection. When the dose was increased, as in rabbits 194 and 191, the symptoms were more pronounced; 150 mg per kilo may be regarded as the minimum dose which produces symptoms of nervous irritability when caffein is injected subcutaneously. Experiments with larger doses were therefore carried out in order to determine the minimum fatal dose. SERIES B. Approximately 0.2 gram of caffein per kilo was employed in these experiments. Diet and race as possible factors which may influence the toxicity of caffein were made the subject of study in these experiments which were divided into two groups as shown in the table, page 25. _Rabbit 95. Gray and white male. Weight, 1,478 grams. Diet, oats._ February 27: 11.30 a. m., 15 cc 2 per cent caffein (210 mg per kilo) injected subcutaneously; 2.20 p. m., no symptoms, tremors observed when handled, but not marked, reflexes slightly increased, no muscular rigidity nor any other symptoms; 2.45 p. m., rabbit suddenly became very restless, jumped off the table, and had convulsions; 3.45 p. m., rabbit died, rigor mortis set in almost immediately after death. _Rabbit 96. Gray and white male. Weight, 1,585 grams. Diet, oats._ February 27: 16 cc 2 per cent caffein (200 mg per kilo) injected subcutaneously at 3.40 p. m.; increased reflexes observed about one hour after caffein was injected, but no other symptoms. February 28: Rabbit found dead. _Rabbit 112. Black female. Weight, 875 grams. Diet, oats._ March 18: 9 cc 2 per cent caffein (205 mg per kilo) injected subcutaneously at 3 p. m.; 3.30 p. m., rabbit became restless, reflexes were increased, tremors were observed, but no other symptoms; 4.15 p. m., rabbit had tremors, was handled but this failed to induce tetanus, 10 minutes later tetanus of short duration with recovery occurred. March 19: 9 a. m., found dead. _Rabbit 119. Yellow white female. Weight, 1,060 grams. Diet, oats._ April 17: 10 cc 2 per cent caffein (188 mg per kilo) injected subcutaneously at 2.10 p. m. April 18: Rabbit found dead.