280 Bayliss and Starling, 



electrical variation; but in the latter case the total duration is only 

 0.18", in the former 0.35", and in the intact dog 0.30". 



We conclude then, that the electrical variation in man and in the 

 intact dog, begins with negativity of the base. This is followed by a 

 phase in which negativity at the apex predominates, and this again by 

 a third phase, consisting of negativity of the base; therefore in man 

 as in the exposed heart of the dog, the ventricular contraction be- 

 gins at the base and travels to the apex in the form of a wave, but 

 in the former case the excitatory state at the base outlasts that at 

 the apex. 



Description of the Plates XV— XVII. 



Plate XV. 



All ciirves to he read from left to right. 



Fig. 1 , 2 , 3. Different forms of the diphasic normal curve. Apex and base led 



off. Warmed air in respiration. Base negativity precedes apex negativity. 



Time-trace Vs"- (Bfise to acid. Apex to capillary.) 

 Fig. 4. Normal curve. Warmed air. Base negativity followed by apex negativity. 



Time Vs"- (Bfise to acid. Apex to capillary.) 

 Fig. 5. Same heart, warmed air replaced by cold, transition stage. 

 Fig. 6. Same heart, further action of cold in causing complete reversal, apex 



negativity followed by base negativity. 



Fig. 7. Same heart, warm air replaced. Return to original condition of base 

 negativity followed by apex negativity. 



Fig. 8. Base and apex of inner sixrface of left ventricle led off. Cold air. Apex 

 negativity followed by base negativity. Time-trace ^/g". (Base to acid. 

 Apex to capillary.) 



Fig. 9. CuiTe showing short equipotential interval. (Base to capillary. Apex to acid.) 



Fig. 10. Curve with longer equipotential interval. Time-trace in both. ^/g". (Base 

 to acid. Apex to capillary. 



Fig. 11. Variation of spontaneous beats in frog heart, to show absence of equi- 

 potential interval. (Connections as in 10.) 



Fig. 12 and 13. Similar curve from tortoise ventricle. Time -trace in seconds. 

 (Connections as 10.) 



