February 23: Still alive, in good condition.

Rabbit 581. Gray female. Weight, 1,680 grams.

February 14: 3.45 p. m., 17 cc 2 per cent caffein solution injected into the lumbar muscles of the right side; 4 p. m., reflexes increased; 4.15 p. m., jumped off the table and had wild convulsions, became very restless, walked about the laboratory; 4.25 p. m., had convulsions occasionally; 4.30 p. m., extremities extended and quite rigid; 4.35 p. m., convulsions and death.

Rabbit 582. Gray male. Weight, 1,870 grams.

February 14: 4.15 p. m., 18 cc 2 per cent caffein solution injected into the lumbar muscles of right side; 5 p. m., reflexes increased; walked about in the room, then rested; 5.15 p. m., had short spasm when handled.

February 23: Alive; good condition.

The data presented in these experiments show that the toxicity of caffein when injected into the muscles of the lumbar regions is the same as when injected into the gluteal muscles. The rabbits of series A received approximately 0.2 gram caffein per kilo and two died as a result of this treatment. The other two survived but symptoms of caffein intoxication were observed.

In series B smaller doses proved fatal, from which it would appear that caffein is more toxic when injected into the lumbar muscles. Further observations, however, failed to corroborate the results obtained in this series. Thus, in series C, 130 to 150 mg of caffein per kilo injected into the lumbar muscles produced mild symptoms only. Experiments with larger doses showed that 0.180 gram caffein per kilo may cause death. It will be noticed, on the other hand, that rabbit No. 455 survived a dose of 0.2 gram per kilo. New experiments were therefore carried out in which the same amounts of caffein in proportion to the weight of the animals were injected into the lumbar muscles as into the gluteal muscles. As shown in the experiments of series D, one rabbit (No. 581) died shortly after caffein was injected into the lumbar muscles; two recovered. Two of the three which received injections into the gluteal muscles were found dead the next day; one recovered. Post-mortem examination failed to indicate the presence of any abnormalities. The rate of absorption of caffein from the gluteal and from the lumbar muscles seems to be, therefore, the same, or not to differ very much. The observations of Auer and Meltzer[7] are of interest in this connection. According to their investigations adrenalin is more rapidly absorbed from the lumbar than from the gluteal muscles. This is in all probability due to the greater delicacy of the test they employed (since they judged the rate of absorption by the effect of adrenalin on blood pressure) as well as to the much greater activity of the substance.

Table 4.—Intramuscular injections.

SERIES A.
No. Weight.Caffein per kiloSymptoms after—Duration of life. Site of injection. Remarks.
Grams. Gram.
284 1,100 0.200  3 hoursLess than 20 hours GlutealWhite and brown female.
286 1,315 .1977 2 hoursSurvived do.White and black female.
285 1,385 .200  Present do. do.Yellow and white female.
287 1,140 .210 15 minutes25 minutes do.Gray female.
SERIES B.
307 1,175 0.136 5 hours6 hours, 20 minutes LumbarGray female.
306 1,860 .134 3 hours4 hours do. Do.
181 1,230 .130 4 hours5 hours do.Gray.
SERIES C.
425 1,520 0.131 1 hourSurvived LumbarGray.
426 1,405 .14230 minutes do. do.Gray female.
427 1,830 .15350 minutes do. do. Do.
453 1,160 .20030 minutesLess than 20 hours do.Gray male.
455 1,185 .200 do.Survived do.Gray female.
428 1,650 .180Less than 20 hours do.Gray male.
429 1,340 .200 do. do. Do.
SERIES D.
577 1,380 0.20010 minutesLess than 18 hours GlutealGray male.
578 1,670 .210 do. do. do. Do.
579 1,490 .20015 minutesSurvived do.White and gray male.
580 1,510 .200 do. LumbarGray male.
581 1,680 .20015 minutes50 minutes do. Do.
582 1,870 .19245 minutesSurvived do. Do.