274 ELECTRO-PHYSIOLOGY CHAP. 



the muscle, it is sufficient to cause a demonstrable anelectrotonic 

 depression of excitability within the myopolar part of the nerve. 

 With sensitive preparations, the height of the twitch discharged at 



ab by the ascending make induc- 

 tion shock was then regularly less 

 when the region cd was simul- 

 taneously polarised by a branch of 



abed the primary current. To Griin- 



Fl - m hagen's conclusion that the anelec- 



trotonic depression of excitability at ab existed previous 

 to the induction closure, i.e. coincided with the entry of the 

 polarising current, Tschirjew (35) objected that with the 

 combined action of the two currents, the induced exciting current 

 must necessarily be weaker than in the other case, because a part 

 of the inducing current would now be led into the nerve by the 

 rheochord. But this objection is, as Hermann (35) subsequently 

 pointed out, of no weight in view of the relations of resistance ; 

 since it can hardly be of consequence to the current in the 

 primary coil of low resistance (1-2 Siemens' units), whether a 

 branch current, sent into the nerve with its 40,000 to 70,000 

 units, is made or broken, as was also demonstrated experimentally 

 by Baranowsky and Garre (35, p. 449). 



Tschirjew's experiments on the rate of transmission of galvanic 

 as well as excitatory charges in medullated nerve during electro - 

 tonus led him to conclusions fundamentally different from those 

 of his predecessors, and his views were subsequently confirmed 

 by Bernstein in an investigation which we have not yet referred 

 to. He stated that the electrotonic alterations in nerve are 

 transmitted at a rate approximating to that of excitation, but, 

 generally speaking, somewhat lower. 



In order to determine the rate at which the anelectrotonic 

 decrease of excitability in the nerve is transmitted, Tschirjew 

 employed a method analogous to that of Wundt. 



" The minimal stimulus which will discharge a twitch is deter- 

 mined at any point of the nerve in a frog's gastrocnemius preparation. 

 A strong ascending current is then made in the part of the nerve 

 proximal to the central end, at a certain distance from the point 

 of excitation. Closure of this current of course evokes no twitch 

 under these conditions. After a certain brief period the excita- 

 bility of the nerve is tested again at the former point. If the 



