and Plants to the Electrical Phenomena associated with it. 47 



have for its photographic counterpart the curve S. May I emphasize 

 the point that if you have the curve F of a parallel-fibred muscle, you 

 •can calculate from it S' and consequently S, but that from S alone you 

 cannot 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 contacts 

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

 muscle first abp then at d, and the consequent movement of the column 

 is photographed (Photo. 1). 



Photograph 1.* 



You recognise that it is the counterpart of the deduced curve S. In 

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

 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 round the muscle between 

 p 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. 2). 



"What has the ligature effected 1 It has exercised no influence on 

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

 so that its effect at p only is manifested, and not that at d. The rela- 

 tion 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 screen together, in such a way that they are in synchronic rela- 

 tion to each other (Photo. 3). 



* Photographs 1, 2, and 3. — jCurarised Sartorius kept for ahout twenty-four 

 hours iu 0*6 per cent, solution of chloride of sodium. Temperature during obser- 

 Tation 9° C. Contacts, &c, as in Diagram 5, but p much nearer to d. 



