326 PROTOPLASMIC ACTION AND NERVOUS ACTION 



from tissue to tissue. This time is exceedingly brief 

 in rapidly responding tissues like voluntary muscle 

 and nerve; for example, in frog's muscle the ''electrical 

 response" has a shorter latent period and a much shorter 

 duration than the ''mechanical response"; the muscular 

 twitch begins (at 20°) about o.oi of a second after 

 stimulation and lasts about o.i second, while (according 

 to Snyder) the latency of the electric variation is about 

 0.003 of a second and its total duration about 0.007 of a 

 second.^ Thus the electric variation may be completed 

 before the muscle has begun to contract; it is the first 

 evident effect of stimulation and apparently is an index 

 or accompaniment of critical changes which determine 

 the succeeding chemical and mechanical processes. 



In general the more rapidly a muscle contracts the 

 briefer is its chronaxie and the more rapidly its bioelectric 

 variation develops.^ There is also a direct correlation 

 between the rapidity of contraction and the rapidity 

 of transmission of the excitation-wave; this is true not 

 only for the transmission in the muscle itself, but also 

 for the transmission in the motor nerve supplying the 

 muscle. 3 Rapidity in physiological action thus implies 

 rapidity in the associated bioelectric processes. A 

 muscle and its motor nerve constitute a single reaction- 

 system, and the rate of the bioelectric processes is a close 

 index of the rate of reaction of the entire system. Trans- 

 mission of the excitation-state from nerve to muscle 

 through the motor end-plate is apparently a phenomenon 

 of the same kind as transmission from region to region 



^ a. CD. Snyder, American Joiirnalof Physiology,'KXXlI(igi2) , ^:^6. 



^ Cf. Lapicque, Jour, de physiol. et de path, gen., X (1908), 601. 



3 Carlson, American Journal of Physiology, 'K, (1904), 401; XV (1906), 

 136. 



