On Electrical Stimulation of the Frog's Heart. 485 



the auricle L. This is in part due to the fact that the auricle has 

 only shared imperfectly in the heating. 



L. 



Stimulation of Ventricle (maximal) . Heart heated about 7° C. Time as in K. 



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

 inrpulse 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), originates a systole there, for then the 



M. 



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



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 "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), but we may find that there 

 is an impulse propagated to the auricle, for this may reduplicate 

 whilst the ventricle remains quiescent (No). 



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



2 c 2 



