612 ELECTRICAL STLMULATION OF THE FKOG'S HEART. 



There is thus a disturbance of both muscle-wave and nervous 

 impulse produced by the heating to which the auricles and 

 ventricle have been exposed. This failure on the part of the 

 ventricle occurs only after there has been a reduplication of its 

 beat, and does not often occur, so far as we have seen, when 

 stimulation, applied to the auricle itself (M Fig. 205), originates 



Stimulation of Auricle (maximal). Heart heated about 6" C. 



a systole there, for then the ventricle follows in due course; 

 we should therefore regard the exhaustion of the ventricle after 

 its unusual activity as the cause of its quiescence after the 

 normal auricular beat. Should stimulation be applied to the 

 auricle during ventricular diastole, a reduplicated auricular 

 beat succeeded by a ventricular at once occurs. In all phases 

 this natural sequence is maintained, though sometimes at the 

 end of its systole the auricular reduplication may be 0"5". 

 Whilst a long pause follows this reduplication, it is very rarely 

 that a stimulation of the auricle produces omission of the 

 succeeding auricular and ventricular reduplication. 



In stimulating the venous sinus, however, omission of the 

 following ventricular beat is frequently produced when the 

 shock falls at the commencement of ventricular systole (Nj 

 Fig. 206), but we may find that there is an impulse propagated 

 to the auricle, for this may reduplicate whilst the ventricle 

 remains quiescent (N2). 



A little later, and up to the maximum of systole, the auricular 

 reduplication is succeeded by a ventricular (Ng), and after the 

 maximum, and during the diastole of the ventricle, the induced 

 auricular beat may occur synchronously with the ventricular, or 

 it may precede it in regular course. 



Both of the charts N^ and N^ (Fig. 206) are taken from a 



