EFFECT OF ATROPINE 



131 



After about a minute had elapsed atropine solution was dropped on to 

 the heart, commencing at n, fig. 103. After an interval a small contraction 

 of the ventricle occurred, - v - 7 ---■= 



and gradually this in- .»••»/.'.. -at, v 



creased in force and fre- 

 quency until the charac- 

 ter of the beat was once 

 more regained. It is 

 also seen that the force 

 of the auricular beat 

 was regained, though 

 more slowly than the 

 ventricular. In about 

 the middle of this tracing 

 the rate of conduction 

 of the contraction wave 

 from auricle to ventricle 

 is seen to be slow, and 

 from that time on to in- 

 crease, until finally it 

 became very rapid. 

 Atropine, then, favours 

 the conduction of the 

 contraction from auricle 

 to ventricle. Tracing 

 in shows that stimula- 

 tion of the left vagus 

 with strong tetanising 

 shocks thrown in from 

 a to b produced no 

 inhibition nor change of 

 force. In iv the sinus 

 was stimulated. This 

 also proved ineffectual, 

 though, previously, 



stimulation of both 

 vagus and sinus pro- 

 duced the usual inhibi- 

 tion. These inhibitory effects are reproduced 

 taken just before muscarine had been applied. 



Experiment 2. — To a fresh heart arranged as in the previous experimenl 

 apply a few drops of a h per cent, solution of pilocarpine nitrate. It acts 

 similarly to muscarine, and its effect is abolished by atropine. 



k 2 



