Since two controls survived the same dose in proportion to the body weight of the animal without showing any symptoms, the assumption is justified that the lower resistance to caffein was due to the presence of pneumonia, thus affording additional support to the view that the toxicity of caffein may be increased in disease. INJECTION INTO THE PERITONEAL CAVITY. These experiments were carried out on full-grown and on young subjects. As in previous experiments, doses of different sizes were employed. A dose of 0.2 gram per kilo was tried first and then reduced gradually to 0.1 gram per kilo. _Cat 10. Female. Weight, 2,970 grams._ October 9, 1909: 1.30 p. m., 30 cc 2 per cent caffein (0.2 gram per kilo) injected into the peritoneal cavity; urine examined for albumin and sugar, negative; cat found dead at 2.30 p. m. No urine in the bladder. _Cat 16. Black female. Weight, 2,420 grams._ October 9, 1910: Urine examined for albumin and sugar, negative; 2.30 p. m., 22 cc 2 per cent caffein (0.183 gram per kilo) injected into the peritoneal cavity; found dead at 3 p. m. _Cat 99. Well-fed gray female. Weight, 3 kilos._ June 22, 1911: 3.40 p. m., 15 cc 2 per cent caffein injected into peritoneal cavity; salivation and marked irritability within one hour after injection. June 24: Alive, appetite good. _Cat 98. Well-fed black male. Weight, 4,100 grams._ June 22: 3.45 p. m., 20.5 cc 2 per cent caffein (0.1 gram per kilo) injected into peritoneal cavity; very irritable a few minutes after injection, no other symptoms. June 24: No symptoms, appetite good. _Cat 93. Black and white. Weight, 1,450 grams._ June 22: 3 p. m., 30 cc 2 per cent caffein (0.137 gram per kilo) injected into peritoneal cavity; salivation, no other symptoms; under observation until 6 p. m. June 23: 9 a. m., no urine, cat showed no symptoms. June 24: 9 a. m., no symptoms, took nourishment as usual. _Cat 87. Well-fed white female. Weight, 2,615 grams._ June 23: 2.45 p. m., 19 cc 2 per cent caffein (0.145 gram per kilo) injected into peritoneal cavity; became irritable and restless. June 24: 9 a. m., no symptoms, took nourishment as usual. _Cat 97. Gray. Age, 3 months. Weight, 500 grams. Diet, meat._ June 24: 2.25 p. m., 5 cc 2 per cent caffein (0.2 gram per kilo) injected into peritoneal cavity; 4 p. m., no symptoms. June 29: Died. _Cat 96. Gray and white. Age, 3 months. Weight, 575 grams. Diet, meat._ June 24: 2.20 p. m., 4 cc 2 per cent caffein (0.139 gram per kilo) injected into peritoneal cavity; 3.55 p. m., no symptoms. June 30: Died. _Cat 95. Black. Age, about 3 months. Weight, 860 grams. Diet, meat._ June 24: 10.15 a. m., 8.6 cc 2 per cent caffein injected into peritoneal cavity, salivation immediately after injection; 10.25, convulsions and paralysis; died 10.45 a. m. _Autopsy_: Macroscopical examination of the organs, negative. _Cat 94. Black and white. Weight, 790 grams. Age, about 3 months. Diet, meat._