278 



ELECTRO-PHYSIOLOGY 



CHAP. 



excitation) usually coincides with the beginning of the katelectro- 

 tonic variation, and is inseparable from it. 



From these experiments, as well as from the earlier observa- 

 tions of Tschirjew, it would appear that the entrance of the 

 katelectrotonic current at the point of leading off docs not coincide 

 in time with the closure of the polarising current, and that the 

 underlying alteration of the nerve diffuses more slowly than the 

 wave, of excitation which precedes it. This separation of the 

 two apices is only seen distinctly when the tract of nerve led 

 off is sufficiently remote from the polarised tract, since both 



FIG. 211. 



processes appear to begin simultaneously at the kathode, i.e. at 

 the moment of closure, and, according to Bernstein's view, can 

 only be separated after further propagation. The absolute rate 

 at which the katelectrotonic alteration is transmitted can there- 

 fore hardly be determined exactly from such experiments. 

 Bernstein estimates it at about 910 in. per sec. The develop- 

 ment and diffusion of galvanic anelectrotonus is shown by the 

 same method to be essentially similar, when the excitation by 

 the rheotome is effected (by reason of the led -off transverse - 

 section of the nerve) with ascending currents. Even with strong 

 currents there is invariably a much smaller negative initial varia- 

 tion (excitatory wave) than with descending excitation, along 

 with which there is a positive anelectrotonic deflection increasing 



