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. ----+--------+-------+----------+-----------+----------+-------------- | |Caffein| | | | No.| Weight.| per | Symptoms | Duration | Site of | Remarks. | | kilo | after-- | of life. |injection.| ----+--------+-------+----------+-----------+----------+-------------- |_Grams._|_Gram._| | | | 284| 1,100 | 0.200 | 3 hours |Less than | Gluteal |White and | | | | 20 hours | | brown female. 286| 1,315 | .1977| 2 hours |Survived | do. |White and | | | | | | black female. 285| 1,385 | .200 | Present | do. | do. |Yellow and | | | | | | white female. 287| 1,140 | .210 |15 minutes|25 minutes | do. |Gray female. ----+--------+-------+----------+-----------+----------+-------------- SERIES B.