ACTION OF XICOTTXE 



301 



affected? Apply more of the drug and observe the later 

 action on the heart. What is the innervation of the heart 

 (Fi-. 222) 1 



Fig. 267. Prop heart tracing showing the action of nicotine. The vagus trunk 

 was stimulated as indicated. In the normal (lower) tracing inhibition occurs but after 

 nicotine (second tracing) no inhibition follows. How do you explain this? Stimulation 

 of the crescent in the next two lines still is followed by inhibition. The final effects 

 of the drug are shown in the last two (upper) tracings. 



EXPERIMENT LXXIII. 

 Nicotine. (Turtle: Heart and Vagus Nerve.) 



1. Eepeat the above experiment on a turtle which is a 

 more satisfactory animal for the experiment than is the 

 frog. Why ? 



