338 MOTION IN ANIMALS AND PLANTS. 



passing from p to d. It will be seen at once why we call this effect 

 the diphasic viiriation. 



I explained before that in accordance with the fundamental proper- 

 ties of our instrument the curve P' would have as its photographic 

 expression the curve P. Similarly the combination curve S<' would 

 have for its photographic counterpart the curve aS'. May I emphasize 

 the point that, if you have the curve P' of a parallel-fibered muscle, 

 you can calculate from it 8' and consequently S^ but that from <S' alone 

 3^ou can not deduce the others. In other words, if you know the form 

 of P\ you know everything as to the form of the electrical response — 

 the Reizwelle. 



Let us now take the actual result. As before stated, the two con- 

 tacts are at p and d^ and the muscle is excited at r. The wave affects 

 the muscle first at jf>, then at r7, and the consequent movement of the 

 column is photographed (photograph 1, PI. I). 



You recognize that it is the counterpart of the deduced curve -iS'. In 

 other words, it is the expression of the effects of two similar processes 



Duujram S. 



having their seats at the two contacts. Our aim must now be, as I 

 have explained, to annul or suspend the effect of one of them, leaving 

 the other intact. The method is simple. After having obtained the 

 record I have shown you, I tie a fine thread around the muscle between 

 2J and d. I tighten the ligature so as to constrict the muscle and again 

 record the variation. There is no change of effect, for the wave is 

 still able to pass the constriction. I tighten again; it still passes. I 

 then draw the ends of the ligature hard, and again photograph. I find 

 the photographic curve is no longer S but P, i. e., it has assumed 

 the characteristic form of the monophasic electrometer curve (photo- 

 graph 2, PL I). 



What has the ligature effected? It has exercised no influence on 

 either contact, but it has arrested the progress of the excitatory wave, 

 so that its effect at^ only is manifested, and not that at d. The relation 

 between the two curves {P and S) is obvious enough when they are 

 seen in succession. It will be still more obvious if I place them on the 



