220 EXPERIMENTAL PHARMACOLOGY 



EXPERIMENT XXXII. 



Strychnine. (Frog: Heart and Vago- sympathetic 



Nerve.) 



1. Pith a frog and destroy the spinal cord with a soft 

 copper wire. Examine the beating of the lymph hearts 

 (see Fig. 66) before and after the cord is destroyed. How 

 is the beat of these affected? Fasten the frog down, ven- 

 tral side upward, and dissect out the vagus nerve (Fig. 60). 

 Arrange to record heart tracings on a moderately slo\v 

 drum (Fig. 63). Take about one inch of normal tracing 

 and then stimulate the vago-sympathetic nerve and record 

 the inhibition and recovery. Take two inches more of the 

 normal record and repeat the stimulation. Lower the 

 drum and start a second round. Drop on to the heart a 

 few drops of strychnine sulphate solution (one cubic centi- 

 meter equals one-half milligram) and after a few seconds 

 again stimulate the nerve. This stimulation record should 

 be directly above the first inhibition record in the first 



/ 



round on the drum. Apply more drug to the heart and 

 stimulate again. Be sure the stimulating current is not 

 too strong and do not continue its application to the nerve 

 any longer than is absolutely necessary or the nerve (or 

 its endings) may be affected. Apply more drug and then 

 stimulate again. How is the beat of the heart affected? 

 Is the muscle of the heart directly concerned in this? What 

 are the later effects of strychnine on the heart when thus 

 applied? How does strychnine affect the innervation of 

 the frog's heart? 



EXPERIMENT XXXIII. 

 Strychnine. (Turtle: Heart and Vagus Nerve.) 



1. Pith a turtle and fully destroy the cord by pushing 

 a soft copper or iron wire (No. 14 or 16) down the spinal 



