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EXPERIMENTAL PHARMACOLOGY 



AVliat structures are involved in this action ? Keep taking 

 records and watch for a characteristic grouping of the 

 beats in fours, threes, twos, etc. The drug is especially 

 liable to produce this result. 



What action would nicotine or lobeline or pilocarpine or 

 strychnine have on the frog or turtle heart after cocaine 

 had produced its first effect on the organ? Is this action 

 the same in the mammal? Explain. 



Fig. 301. Frog heart tracing showing the later effects of cocaine. Note the group- 

 ing of the beats. The earlier effects on the innervation of the heart are not shown in 

 the tracing. 



EXPERIMENT XCVI. 

 Cocaine. (Frog: Action on Muscular Work.) 



1. Arrange your apparatus as shown in Fig. 224. Pith 

 a frog and ligate the right thigh tightly to stop the circu- 

 lation in the corresponding gastrocnemius muscle. Into 

 the dorsal lymph sac inject one cubic centimeter of cocaine 

 solution (one cubic centimeter equals two milligrams). 

 Arrange the frog with its right gastrocnemius muscle at- 

 tached to the lever as shown in the picture. The secondary 

 wires are made of very fine flexible copper and carry the 

 current directly to the muscle. Keep the muscle damp 



