On Electrical Stimulation of the Frog's Heart. 475 



ventricular beat (fig. 26). Inhibition of the ventricular systole has 

 not been found in many of the hearts examined, though it occasion- 

 ally occurs. 



Fia. 26. 



Stimulation of Venous Sinus (maximal). 



Should the exciting shock fall at such a time as to cause an 

 instantaneous auricular systole, we find this systole is nearly syn- 

 chronous with that of the ventricle, and that the latter has a short 

 latency, but should the shock fall so that the auricle responds by a 

 genuine contraction, the ventricular reduplication follows with a long 

 latency. 



Inhibition of the ventricular with reduplication of the auricular 

 beat may result occasionally from stimulation of the venous sinus. 



Appendix A. Cooled Heaet. 



The construction of a simple piece of apparatus has enabled us to 

 obtain curves much more striking than those which appeared in the 

 foregoing paper, as they represent a far greater variation of tempe- 

 rature. 



Instead of the gutta-percha support for the heart already described, 

 a hollow copper pan of similar shape was employed. It was provided 

 with influx and efflux tubes, and insulated below by a plate of ivory in 

 which ran also the electrodes destined for the stimulation of the sinus. 

 This was connected with the usual support passing over the body. 

 Upon minimal stimulation of the ventricle itself the succession of 

 auricular and ventricular contraction is illustrated in the charts A 1-4 

 here inserted . It is seen that the action of cold modifies considerably 

 the relation between the ventricular contraction and the succeeding 

 auricular beat. In A 2 we find a reduplicated ventricular beat suc- 

 ceeded by a normal auricular contraction. 



In A 3 cooled through about 2*5° C, the ventricle responds to the 

 same stimulation, and the wave does not pass upward to the auricle ; 

 and in A 4 , in which the contraction and relaxation of the heart had 

 become very slow from a further reduction of 2°, we find the auricular 

 rhythm is regular in spite of ventricular reduplication. There is in 



