HEATED HEART-STIMULATION OF VENTRICLE. 593 



on in the systole the stimulation is applied, the shorter is the 

 latent period, and the more perfect the reduplicated contraction. 



Stimulation of the Venom Sinus — Maximal. 



Omission may be caused by stimulation applied at the com- 

 mencement of systole, or reduplication may occur in all phases 

 (Fig. 181). 



Eeduplication has the longest latency at the commencement 

 of systole, and there is true auricular precedence up to or 

 beyond the maximum in this phase. In the decline of systole, 

 after the maximum is passed, and the abscissa has been nearly 

 reached, there is occasionally reduplication with short latency, 

 the auricular and ventricular contraction being synchronous. 



Action of Heat on the Heart. 



In this series of experiments the pithed frog in which the 

 brain and spinal cord had been destroyed, was laid upon a 

 metal plate, the temperature of which was gradually raised by 

 means of a flame beneath it. 



Ventricular Stimulation — Minimal. 



The refractory phase is generally wanting in the ventricular 

 systole, but it may be present in exceptional cases, not unfre- 

 quently in the same tracing in which stimulation most generally 

 produces reduplication (Fig. 182). 



It may be noted that irregularity of response to stimulation 

 is one of the characteristics of the heated condition. Stimula- 

 tion usually causes reduplication. Should stimulation fall at 

 the commencement of ventricular systole, no effect is produced 

 tni the whole cycle of the systole has been passed through, when 

 reduplication by a very perfect systole occurs. Latencies 

 diminish in proportion as the stimulation occurs later in the 

 systole of the heart. Eeduplication occurring in response to 

 stimulation falling at the maximum is often demonstrated by a 

 beat origiaating when the relaxation after systole is completed, 

 and therefore distinct from the original beat : this is due to the 

 fact that the curve of the heated heart is much shorter in 



2 Q 



