336 INHIBITION BY EXCITATION AND 



are obtained which are essentially the same, whether the excitation is 

 effected by an induction-shock acting anywhere along the muscle, or 

 by the shortest possible closure of a battery-current in either direction. 

 In both cases, the wave of contraction remains, so to speak, arrested 

 on its way through the muscle and produces tetanus which con- 

 tinues for a longer or shorter time at about the same strength. 

 When we consider the hitherto complete absence of proof of the 

 discontinuous nature of this contraction, it will be better to describe 

 it as a 'tonic ' shortening of the muscle in all its parts. 



As von Bezold and Fick have already remarked, various forms of 

 the contraction of veratrine muscle can be distinguished, of which 

 I mention only one of those of most frequent occurrence, viz. that 

 in which the proper tonic persistent contraction is preceded by an 

 initial twitch of short duration. In this case, just as I have 

 described after section of the nerve, there occurs at the moment 

 of excitation a rapid contraction of the muscle to a maximum ; this 

 is immediately succeeded by a considerable elongation, followed 

 closely by another slow contraction which gradually gives way to 

 relaxation. 



I have hardly ever failed to observe indications of this character- 

 istic mode of shortening, especially after the preparation has lain 

 a long time in dilute solution of common salt. As Fick has already 

 shown, it is out of the question to explain the initial twitch 

 mentioned, by an indirect excitation of the muscle through the 

 intermuscular nerves, and to refer the succeeding persistent con- 

 traction to direct excitation of the muscle exclusively ; for just the 

 same forms of curve are observed after previous curarising. The 

 phenomenon may possibly be accounted for by what Griitzner l has 

 recently asserted as to muscle being composed of two kinds of 

 fibre, morphologically and physiologically different, corresponding 

 to red and white muscles. We may perhaps consider as in support 

 of this view, the fact that the same sort of contraction-curves with 

 two apices are not unfrequently observed under other circumstances 

 e. g. after treating locally with Na 2 CO 3 , or even in quite normal 

 curarised muscles. Griitzner 2 goes so far as to believe, that such 

 curves represent the rule for the fresh sartorius of the frog. 



The form of shortening just discussed does not seem the most 

 favourable for the experiments to be described. A more suitable 

 form is that in which the contraction, at first rapid, is gradually 



1 Recueil zoologique Suisse, vol. i. No. 4 (zur Anatomic u. Physiol. quergestr. 

 Muskeln). a Loc. cit. p. 675. 



