1906.] Special Excitable Substances in Cells. 177 



-4.mgs. SO rn.gs 



nicotine curari 



Fig. 4. — Abolition by curari of the contraction in the gastrocnemius muscle of the fow 

 caused by nicotine. The lowest line marks intervals of 10 seconds. 



The amount of curari given is two to three times the amount required to 

 prevent the sciatic causing contraction of the muscle, nevertheless, the 

 injection of 50 milligrammes of nicotine about three and a half minutes 

 later caused the strong contraction shown in fig. 5, and this contraction in 

 turn was reduced nearly to zero by a further injection of 50 milligrammes 

 of curari* (fig. 5). A second injection of 50 milligrammes of nicotine 



UWHU 



Fig. 5.— Continuation of tracing given in fig. 4. Mutual antagonism of nicotine and 

 curari. The 5 c.c. of salt solution was injected to show that the injection 

 itself did not cause relaxation. Time marked in 10 second intervals. 



10 minutes later was almost without effect, the substance stimulated by 

 nicotine being temporarily paralysed, but the muscle readily contracted on 

 direct electrical stimulation. 



Experiment, then, with curari does not confirm the obvious view as to the 



* Large amounts of curari are apt to weaken or stop the heart, but control experiments 

 show that the nicotine contraction continues unaltered for several minutes after complete 

 cessation of the heart beat, and that the curari relaxation occurs when the blood pressure 

 is unaffected by the injection. 



