62 Prof. J. Burdon-Sanderson. Relation of Motion in Animals 



Photographs 13 and 14.* 



muscle in the longer duration of the period which intervenes between 

 culmination and decline, and consequently bears a greater resemblance 

 to the effect of a short continuous excitation of muscle than to that of 

 an instantaneous one. 



Turning to the diphasic variation obtained when the surface under- 

 lying the distal contact is not devitalised, we see that during the whole 

 intervening period just referred to, the two contact surfaces are ap- 

 proximately equipotential. This of course does not mean that both 

 are physiologically inactive, but simply that the influence of the one 

 exactly balances that of the other. This meaning of the diphasic 

 variation is (with the exception of the initial spike) that which was 

 assigned to it in 1882. It results from the mutual interference of two 

 monophasic variations, the dip of the curve at the end indicating that 

 the effect of the distal contact overlasts that at the proximal. 



The general result of these observations is that, just as from the 

 mechanical point of view the systole of the ventricle has lately been 

 shown to be entirely analogous to the response of a muscle to an in- 

 stantaneous stimulus, provided that we substitute volume for length 

 and lateral pressure for tension,! so as regards the electrical phenomena 



* Ventricle of hea"t of R, esculenta arrested by Staminas' ligature. Exciting 

 electrodes on auricle. Leading off contacts at base and apex. In 13, apex 

 surface devitalised by heat ; in 14, both surfaces uninjured. 



f O. Frank, " Zur Dynamik des Herzniuskels," 'Zeits. f. Biol.,' vol. 32, p. 370. 



