Drs. T. L. Bruntoii and T. Cash. 



Stimulation o Yenous Sinus (maximal). 



reduplication is succeeded by a ventricular (N* 3 ), and after tlie 

 maximum, and dnring the diastole of the ventricle, the induced 

 auricular beat may occur synchronously with the ventricular, or it 

 may precede it in regular course. 



Both of the charts and N 2 are taken from a heart warmed 

 through about 5° C, and N 3 gives a tracing of the same, in which 

 stimulation does not occur. 



In the stronger tendency to cause omission of a ventricular beat, 

 as well as in the frequent occurrence of an auricular contraction 

 coincident with or succeeding the ventricular, when stimulation fails 

 after ventricular maximum or in diastole, we see a marked contrast 

 in the reaction of the venous sinus and the auricle to stimulation. 



From the charts O x , 2 , 3 we see that the latency of the auricular 

 beat varies. Thus stimulation occurring just at the end of auricular 

 relaxation (O x ) causes an instantaneous reduplication, whilst during 

 diastole proper it has a reduplication with a latency of *2". In the 

 former case auricular induced systole precedes the ventricular, in the 

 latter they occur at the same moment (0 2 , 3 ). 



Contrast this result with the stimulation of the auricle itself in 

 which reduplication occurs at once on stimulation, and ventricular 



