218 



ELECTRO-PHYSIOLOGY 



CHAP. 



The effect of partial destruction by heat is much more 

 pronounced than that of mechanical injury, since after the 

 application of a " thermic transverse section " the excitability of 

 the muscle to currents of medium intensity is in every case 

 entirely, or almost entirely, abolished, when the effective electrode 

 happens to be at the end that is in heat-rigor. Since both 

 mechanical injury and thermic destruction produce a swelling of 

 the end of the muscle, as well as other disturbances of the regular 

 processes of the fibres, it is desirable to employ a method which 



1 100 



i m: 



B 



FIG. 88. Twitch curve of sartorius fixed in the middle and stretched in the double myograph. 

 (f7=under, = upper half of the muscle.) Effect of injury (death) of one (the lower) end of 

 the muscle. The pair of twitches, A, were recorded before, B, after injury. 



will kill the muscle, while avoiding these injuries as far as 

 possible. Such is local freezing, according to Kuhne's method, in 

 which the form of the muscle -end scarcely alters perceptibly. 

 If, in addition to this, the muscle is immersed in some indifferent 

 fluid traversed by parallel lines of current, the methods of Engel- 

 mann (22) and Bernstein (16) will be still more exactly carried 

 out in this experiment, since the effect of the asymmetrical form 

 of the muscle is here totally excluded. 



The preceding experiments of time measurement prove that 

 induced currents have the same effect upon striated muscles as 

 constant currents of very short duration, and accordingly that 



