478 



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



Auricular Stimulation. 



Many additional experiments upon cooled hearts have tended to 

 show that it is very rarely that stimulation of considerable strength 

 calls forth a ventricular beat, preceding or coexistent with the 

 auricular. Usually at all phases of stimulation which cause a re- 

 duplication of the auricular beat, the ventricular succeeds in normal 

 relationship (B 1 and 2). There is an exception to this, however, 

 which is frequently demonstrated ; this is, that whilst the auricular 

 beat is reduplicated the ventricular is not, but is succeeded by a long 

 diastolic pause (B 3 ), after which the auricle takes up its old rhythm. 

 Still more rarely stimulation just before commencement of ventricular 

 systole causes omission of both succeeding auricular and ventricular 

 beats (B 4 ). 



The latency of reduplication varies considerably in minimal stimu- 

 lation of the auricle, but this variation is not so much owing to loss 

 of time in the auricular as in the ventricular reduplication. Thus in 

 € x stimulation at the end of auricular relaxation, ventricular latency 



Or 



C 2 to C 3 . Levers as in A. Auricular Stimulation (minimal) of Cooled Heart. 



is l" m 2, in 2 stimulation halfway to ventricular maximum latency 

 is 1", and in C 3 , when stimulation is at ventricular maximum, the 

 latency is for the ventricle only 6". 



On the other hand, more powerful stimulation of the auricle causes 

 reduplications of the ventricle, which are at all times of equal or of 

 very slightly differing values. Thus in a heart much cooled (D 1 

 and 2) we have towards the commencement of ventricular systole and 

 towards the end of relaxation a latency for the induced ventricular 

 beat of 1"'2. 



