COOLED HEART-STIMULATIOIJ OF VENOUS SINUS. 60? 



Gj Duration of contraction l"-4 Length of pause from 



stimulation ... 4" -2 



Cxg If ^ ••• J- *y •» » 5 *o 



G, , 2"-2 ,. „ 6"0 



G, „ „ ... 2"-4 „ „ 6"-2 



Gg was obtained from a heart cooled for a considerable time, 

 and shows a remarkable prolongation of the systole and diastolic 

 pause. 



Gg Duration of current 4" '4 Length of pause from 



stimulation ... 10" 



It will be seen in all these cases that there is a certain 

 relationship between the length of the contraction and of the 

 pause. 



The reduplication of the ventricular beat varies in regard to the 

 time of stimulation under minimal stimulation. Thus in H (Fig. 

 199) when stimulation falls near the commencement of systole, 

 auricular reduplication occurs in 1'''8 and ventricular reduplica- 

 tion in 3"'2. But in the same heart a stimulation during a 

 period of relaxation yielded an instantaneous auricular re- 

 sponse, the ventricular reduplication occurring I'^'S after 

 stimulation. 



In the case of maximal stimulation, the usual result is an 

 instantaneous auricular systole succeeded by a ventricular. 

 The latter, therefore, has a latency equal to the auricular beat : 

 this is seen in Ij, 1^ (Fig. 200), in both of which the latency is 

 about 0*7" ; but in I^ we have, on the other hand, no auricular 

 reduplication for I'^'l. In both this instance and Hj stimulation 

 occurred at the commencement of ventricular systole 



