January 31: 2.30 to 2.37 p. m., 7 cc 2 per cent caffein injected from the burette at the rate of 1 cc per minute; 2.37 p. m., flow of liquid ceased, veins were engorged and bled freely, injection was continued by means of a syringe; 2 cc 2 per cent caffein injected in two minutes; injections discontinued as convulsions appeared; 2.50 p. m., rabbit raised itself but fell over; 3.10 p. m., rabbit assumed normal attitude, walked about the floor without manifesting any signs of the effects of caffein; 4.30 p. m., walked about, gait normal, condition seemed to be good.
February 1: 2 p. m., condition good, appetite good, total amount of caffein injected, 9 cc 2 per cent solution, or 114 mg per kilo.
Rabbit 558. Gray, female. Weight, 1,590 grams.
January 31: 3 p. m., given 8 cc 2 per cent caffein in eight minutes; 3.10 p. m., violent convulsions; 3.20 p. m., rabbit was stretched out on his abdomen, extremities extended, urinated; 4.30 p. m., looked normal; was able to walk about.
February 1: 2 p. m., condition good, appetite good.
Rabbit 292. Belgian hare, male. Weight, 1,770 grams.
February 18: 4.26 to 4.39 p. m., 12.5 cc warm caffein solution (0.141 gram per kilo) injected into ear vein, convulsion followed when this quantity was injected, tonic rigidity of limbs followed soon after; 4.52 p. m., condition unchanged, rabbit on floor, limbs stretched out, and lying on abdomen.
Rabbit 294. Belgian hare, female. Weight, 1,350 grams. Carrot diet for about 10 days before the experiment.
February 19: 12.20 p. m., 5 cc 2 per cent caffein (74 mg per kilo) injected into ear vein in five minutes, edema of the ear, other ear used, 3.5 cc injected in 10 minutes, repeated convulsions; 1.25 p. m., rabbit still alive, frequent attacks of convulsions; 2.30 p. m., found dead. Total amount injected in 15 minutes, 8.5 cc, or 0.126 gram per kilo.
It will be observed in the preceding experiments that symptoms of severe intoxication were present in all of the six rabbits, but only two of these (Nos. 294 and 556) died from the effects of caffein. Of those which survived, three received doses of 100 to 114 mg caffein per kilo, and another (No. 292) received 141 mg of caffein per kilo. The death of rabbits Nos. 294 and 556 may be regarded therefore as a case of exceptionally low resistance to caffein.