From the results of the experiments by intravenous injection summarized in the table, it appears that the minimum toxic dose for rabbits of a 2 per cent caffein solution, injected at the rate of 1 cc per minute, is about 50 mg per kilo. Twice the dose induces severe symptoms and may be fatal; 160 mg per kilo are surely fatal. If the rate of injection is diminished, the toxicity of caffein is lessened, but this effect is not marked unless the injections are very slow. Dilution of the caffein solution suppresses to some extent the nervous symptoms, but the toxicity, on the contrary, seems to be increased. TABLE 5.--_Intravenous injections._ SERIES A. ----+--------+-------+-----------+-----------+-------+--------------- | |Caffein| | Duration | | No.|Weight. | per | Symptoms. | of life. | Diet. | Remarks. | | kilo.| | | | ----+--------+-------+-----------+-----------+-------+--------------- |_Grams._| _Mg._ | | | | 194| 1,310 | 114 |Present |Survived |Oats |White female. 556| 1,635 | 134 |10 minutes |20 minutes | do. |Gray female. 557| 1,580 | 114 |Present |Survived | do. | Do. 558| 1,590 | 100 | do. | do. | do. | Do. 292| 1,770 | 141 | do. | do. | do. | Do. 194| 1,350 | 126 | do. |10 minutes |Carrots| Do. ----+--------+-------+-----------+-----------+-------+--------------- SERIES B, GROUP I. ----+--------+-------+-----------+-----------+-------+--------------- 562| 1,650 | 200 | |1½ hours |Oats |Gray female. 561| 1,450 | 200 | | do. | do. | Do. 560| 1,620 | 200 |Present |Less than | do. | Do. | | | | 24 hours | | 559| 1,875 | 190 | do. |Survived | do. | Do. ----+--------+-------+-----------+-----------+-------+--------------- SERIES B, GROUP II. ----+--------+-------+-----------+-----------+-------+--------------- 279| 1,320 | 166 | |1 hour | |Gray and white | | | | | | female. 254| 1,285 | 160 | |Survived |Oats |Gray female. 567| | 162 | |About 45 | | Do. | | | | minutes | | 255| | 158 | |Died | | ----+--------+-------+-----------+-----------+-------+--------------- SERIES C.