472 Drs. T. L. Brunton and T. Cash. 



dose of strychnia was then introduced into the dorsal lymph sac. As 

 soon as the effect of the drug upon the spinal cord was evidenced by 

 distinct spasm, the heart was rapidly exposed, placed on the car- 

 diograph, and stimulation applied. The same order will be observed 

 as in the description of the experiments on the normal heart. 



Stimulation of the Ventricle — Minimal. 



On applying a minimal stimulus to the strychnia heart (fig. 20) 

 we were struck, in the first instance, by the extreme length of the 



Fig. 20. 



Stimulation of Ventricle (submaximal). 



refractory period. Stimulation has usually no effect, not only when 

 applied before the maximum of the systole as in the normal heart, 

 but also in the maximum, and often far into relaxation. After the 

 phase has passed the stage of reduplication ensues. Reduplication 

 is very complete ; its latency becomes diminished as diastole advances. 

 The reduplicated ventricular beat is succeeded by an auricular 

 pulsation. After the customary pause, the heart resumes its wonted 

 rhythm. It is rarely that stimulation falling at the commencement of 

 ventricular systole causes inhibition. If the auricle is unstimulated 

 and its rhythm is unaltered, there is short latency for the ventricular 

 reduplication. If the auricle is stimulated and contracts before the 

 ventricle, there is long latency, but the latter is rarely seen when a 

 refractory phase is present. 



Ventricular Stimulation — Maximal Stimuli. 



In this case no refractory period exists. An inhibitory period exists 

 occasionally but with this exception, all stimulation produces redupli- 



Fig. 21. 



Stimulation of Ventricle (maximal). 



