206 



ELECTRO-PHYSIOLOGY 



CHAP. 



twitch had expired, as long as the closure lasted ; when, on the 

 other hand, it was ascending the lever returned to the abscissa 

 completely after this twitch. By- the same method of experi- 

 ment, moreover, it is easy to establish v. Bezold's conclusions. In 

 two experiments Engelmann found that the closure twitch began 

 0'006 sees, and 0*009 sees, later with an ascending than with a 

 descending current, which must be explained by saying that in 

 the ascending current the contraction discharged at the upper 

 end of the muscle must first be transmitted through a tract of 

 muscle 7 mm. long before it can act upon the lower movable 

 section of the muscle. The localisation of the closing, as well 

 as opening, persistent contraction, is elegantly shown by the 



FIG. 85. 



following method, taken from Engelmann. The curarised 

 sartorius is extended in Hering's double myograph, with non- 

 polarisable electrodes, which in this case are both free. In order 

 to observe the changes of form independently in either half of 

 the muscle, its centre is fixed by a clamp specially constructed 

 for the purpose. This consists of two troughs, not exceeding 5 

 mm. in length, supported by a pillar, and covered with a layer 

 of oil clay (Fig. 71). The clay moulds itself firmly to the 

 shape of the muscle, holding it sufficiently by contact alone, 

 with no perceptible pressure, to prevent a direct transfer of the 

 changes of form from one half of the muscle to the other, without 

 inhibiting the transmission of the excitatory process. The non- 

 polarisable electrodes make it possible to continue the passage 



