HEATED HEAHT-STIMULATION OF VENOUS SINUS. 



613 



heart warmed through about 5° C, and N3 gives a tracing of the 

 same, in which stimulation does not occur. 



N,. 



Stimulation of Venous Sinus (maximal) . 



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 Oj, Og, O3 (Fig. 207) we see that the latency 

 of the auricular beat varies. Thus stimulation occurring just at 

 the end of auricular relaxation (Oi) causes an instantaneous 

 reduplication, whilst during diastole proper it has a reduplication, 

 with a latency of 0*2''. In the former case auricular induced 

 systole precedes the ventricular, in the latter they occur at the 

 same moment (0^, O3). 



Contrast this result with the stimulation of the auricle itseli. 



