In the eight experiments comprising series B rabbits Nos. 567, 254, 279, and 255, which may be designated as Group II, received doses of 162, 160, 166, and 158 mg, respectively. Nos. 562, 561, 560, and 559, which may be designated as Group I, received about 200 mg caffein per kilo. In Group II, which received the smaller doses, one (No. 254) survived. This may be regarded as exceptional, since, as was shown in the experiments of the preceding series, even smaller doses may be fatal. About 160 mg per kilo is, therefore, the smallest surely fatal dose. This might be regarded as a contradiction of the results obtained for rabbit No. 559, but it will be noticed that in this case diuresis was very marked. The results of experiments Nos. 294 and 255 are of interest in this connection, since they indicate that a moderate difference in the rate of injection is without any effect on the toxicity of caffein. The greater resistance to caffein of rabbit No. 559 is in all probability due, therefore, to increased diuresis.
Series C.
In these experiments the minimum toxic dose was determined. The conditions were the same as in the experiments of the other series.
Rabbit 293. Belgian hare, female. Weight, 1,610 grams. Diet, oats.
February 18: 3.40 to 3.43 p. m., 4 cc 2 per cent warm caffein solution injected into ear vein, convulsions when 3 cc were injected, repeated attacks; 4 p. m., raised itself on legs, but fell over immediately and lay stretched on abdomen.
February 19: 9 a. m., rabbit looked normal, apparently recovered.
Rabbit 227. White male. Weight, 2,320 grams.
October 26: 3.29¼ to 3.37½ p. m., injected into ear from burette 6.7 cc 2 per cent caffein, no symptoms; experiment discontinued; survived.
Rabbit 563. Gray female. Weight, 1,650 grams. Diet, oats.