620 ELECTRICAL STIMULATION OF THE FROG'S HEART. 



to propagation of the contractile wave back from the ventricle 

 to the auricle. While these observations appear to show that 

 the propagation of the contractile wave from one cavity of the 

 heart to another is of importance in keeping up the rhythmical 

 sequence, we consider that stimuli are also propagated from 

 one chamber of the heart to another through nervous chan- 

 nels: — thus we find that irritation of the venous sinus will 

 sometimes produce simultaneous contractions of the auricle and 

 ventricle instead of the ventricular beat succeeding the auricu- 

 lar in the usual way. This we think is hardly consistent with 

 the hypothesis that a stimulus consists of the propagation of a 

 muscular wave only from the auricle to the ventricle. 



As additional evidence we may notice the occurrence of an 

 auricular beat followed by absence or inhibition of a ventricu- 

 lar beat as the result of stimulation of the auricle, or venous 

 sinus. Moreover, we have noticed in the heated heart the 

 occurrence of groups of regular beats in the ventricle in con- 

 sequence of a single stimulation applied to it, while the auricle 

 has continued to beat with its ordinary unaltered rhythm un- 

 disturbed by the ventricular excitement. 



It is not however our purpose to do more in this paper than 

 state the results we have hitherto obtained, and we shall there- 

 fore reserve for a future communication the consideration of 

 this and some other questions of importance closely allied 

 to it. 



Another question is the nature of the inhibitory influence 

 exerted by one cavity of the heart upon another. Marey had 

 shown that stimulation of the ventricle during a great part of 

 the refractory period exercises an inhibitory instead of a motor 

 action upon the ventricle itself. It might be supposed then 

 that a stimulus of either kind, whether proceeding from the 

 auricle in the form of a contractile wave, or a nervous impulse, 

 might produce inhibition of the ventricle, provided the stimulus 

 reached it during that part of the refractory period in which 

 stimulation usually causes inhibition. From our observations 

 it seems that the inhibition of the ventricle which may follow 

 stimulation of the auricle is not due to the muscular wave 

 propagated from the auricle and striking the ventricle during the 



