30 PHYSIOLOGY OF MI-< !.!> .\NI> NKIiYES. 



our present purpose uhich is to discover whether or 

 not contraction take- place under certain circumstances 

 it is hardly adapted. It may, therefore, be replaced 

 by another ajiparat us. arranged l,y du Bois-Reymond 

 espe, iall\ - 1', n- experiments during Lectures, and called by 

 him the muscle-telegraph. The muscle is fixed in a 

 vice; its other end is connected by a hook \vith a 

 thread running 1 over a reel. The reel supports a long 

 indicating liand to which a coloured disc is attached. 

 The nuiM-le in shortening turns the wheel and lifts the 

 disc; and this is easily seen e\en from a considerable 

 distance. A second thread, slung over the reel, sup- 

 ports a brass vessel which may be filled with shot, so as 

 to apply any desired weight to the muscle. 



The influences which car.se the contraction of the 

 muscle, such as pinching or smearing with acid, are 

 called irrifiinfx, and the muscle is said to be irritable, 

 because cont raei j, >n can he induced in it by these means. 

 The irritants already spoken of are mechanical and 

 chemical ; they labour under a disadvantage in that the 

 muscle, at least at the point touched, is destroyed, or 

 at least is so changed that it is no longer irritable. 

 There is, however, another form of irritant which is 

 free from this disadvantage. If the vice which holds 

 the upper end of the nmsele and the hook to which tin- 

 lower end is attached are fastened to the two coatii, 

 of a charged Kleistian or Leydeii jar, the charge acts at 

 the moment at \\hich the Connection is formed, and 

 an electric shot k traverses the muscle. At the same 

 instant the muscle is seen to contract . and the disc 

 passes abruptly upward. In order to repeat the experi- 

 ment it would be necessary to re-charge the Klei-tian 

 jar. But similar electric shocks may be more con- 



