BIOELECTRIC PHENOMENA 327 



along the same element. Hence if transmission is a case 

 of secondary electric stimulation by the current of the ^ 

 local circuit, it is clear that rapidity of electromotor varia- 

 tion, implying rapidity of conduction, is necessary in a 

 nerve which excites a muscle by means of the bioelectric 

 circuit formed across the junction between nerve fiber 

 and muscle cell. Lucas has furnished evidence that the 

 motor end-plate in vertebrate muscle has a special 

 chronaxie differing from that of either the nerve fiber 

 or the muscle cell,' but it does not appear that the 

 conditions determining the transmission between nerve 

 and muscle are essentially altered by the presence of 

 this intermediary element. According to Lapicque 

 the blocking action of curare results from an alteration 

 (slowing) of the chronaxie of the end-plate.^ Any two 

 contiguous elements, one of which is excited by the 

 bioelectric variation of the other, must have similar 

 time-factors of excitation; dissimilarity in the time- 

 factors or ''heterochronism" (to use Lapicque's term) 

 would be inconsistent with such transmission. This 

 conclusion is a simple corollary of the general laws 

 of electric stimulation described above; a current 

 traversing an irritable element must have more than a 

 certain duration and rate of change, or it fails to stimu- 

 late. Similarly, the momentary ciirrent at the myo- 

 neural junction, when the excitation-wave traveling 

 along the nerve reaches that region, must have a duration 

 and rate of change corresponding with the chronaxie 

 of the muscle cell. 



^ Lucas, Journal of Physiology, XXXVI (1907), 113. 



2 Lapicque, Compt. roid. soc. bioL, LXXII (1913), 674. Cf. how- 

 ever, the critique by Boruttau in Zentr, Physiol., XXXI (1916), 303. 



