240 



EXPERIMENTAL PHARMACOLOGY 



the first round. How do you explain these effects! Cut 

 the sciatic nerve to the muscle you are using. Is the action 

 of the drug central or peripheral? Stimulate the muscle 

 itself directly a few times with single shocks. AVhat does 



this show ? 



Left Ant Caval vein 



.Right Ant Caval vein 



Preodnq/ionic rreurdn 



Postgongl ionic neuron 



nemaAi 

 Gang lion in 

 walls ofs/nus. 

 venosus 



sAuricu/dr sleptum 



_ from nl 

 Sinus to auricle I Position of 



Hi Auriculo -ventricular 



Ho ok from 

 'Heart lever 



YonBezolds Canal/on 



m Auricular septum /.,, , _ 



| 'didders Ganglion 



in auriculo-ventricular junction 



InfVena cai/a 



.Stimulating electrodes 



in sino-auricular junction [Crescent] 



Sympathetic fibres- dotted lines 



Fig. 222. Diagram to show the innervation of the heart in the frog or turtle. 



EXPERIMENT XL. 



Hydrastine. (Frog: Heart and Vagus Nerve.) 



1. Pith a frog and dissect out the vagus nerve (Fig. 

 60). Arrange to record heart tracings and take one inch 

 of normal record. Stimulate the vagus nerve and get a 

 normal inhibition. Then pour on the heart a few drops 

 of hydrastine sulphate solution (one cubic centimeter 

 equals five milligrams). How does this affect the beat"? 

 Stimulate the vagus nerve again and record the result. 



