MOTION IN ANIMALS AND PLANTS. 349 



rents of short duration have been of so much value to phvsiologists. 

 The moment it was understood that the spike indicated a diphasic 

 variation analogous to that of the muscle I felt that I had the kc}' to 

 the complete understanding of my own previous observations. I was, 

 moreover, able to bring these into complete harmony with those of 

 Professor Engelmann made about the same time with the rheott)me 

 and galvanometer. 



Let me ask j^our attention to the photographic curves of the diphasic 

 and monophasic variations which I have placed one above the other in 

 synchronic relation to each other. It is to be noticed that the move- 

 ment of the recording surface is very slow — about a centimeter a second 

 only. To obtain the monophasic curve you have to place the distal 

 electrode on a spot which has been devitalized by scorching, and which 

 is consequently physiologically inactive, the proximal electrode on the 

 living surface near the junction between auricle and ventricle. The 

 instantaneous stimulation is applied to the auricle some couple of 

 millimeters distant from the proximal leading-off electrode. The 

 Reizwelle is propagated from the auricle to the base of the ventricle 

 and then on to the devitalized spot, so that before it arrives at the con- 

 tact it is extinguished.^ Consequently, the change which is expressed 

 by the electrometer curve takes place exclusivel}^ at the proximal con- 

 tact surface. It differs only from the monophasic variation of skeletal 

 muscle in the longer duration of the pei'iod which intervenes between 

 culmination and decline, and consequentlv bears a greater resemblance 

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

 an instantaneous one. (Photographs 13,14, PI. V.) 



Turning to the diphasic variation obtained when the surface under- 

 lying the distal contact is not devitalized, 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 

 instantaneous stimulus, provided that we substitute volume for l(Migth 

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

 there is a complete analogy between the monophasic and diphasic 



^This mode of observation corresponds to the first fundamental experiment in 

 muscle. 

 ^ 0. Frank, Zur Dynamik des Herzmuskels, Zeits. f. Biol., vol. o2, p. 370. 



