REFRACTORY PERIOD OF NERVE CELLS. 615 



there is no longer a (muscular) response to each excitation, as with lower 

 rates ; and he concludes that the refractory period of the cerebral cell 

 is Ol second. This is in conformity with the experiments of Horsley 

 and myself, already alluded to (p. 613), who found the rate of response 

 to cortical excitation in the monkey to be only about 12 per second, 

 even when the excitation rate was very much more rapid, and with 

 the conclusions regarding the rate of volitional impulses arrived at 

 independently by v. Kries 1 and myself 2 (about 10 per second). 



It would further appear that it is not possible to perform a succes- 

 sion of voluntary movements such as is involved in the movements of 

 the fingers in playing a musical instrument, or the movements of the 

 mouth in speaking, at a greater rate than this, and Richet found from 

 experiments upon himself that he was unable to " think " words at a 

 greater rate than about 10 to 12 syllables per second. Thus the rapidity 

 of neural processes has a physiological limit imposed upon it by virtue 

 of the refractory period of the nerve cell. 



1 Arch.f. PhysioL, Leipzig, 1886. 



2 Journ. PhysioL, Cambridge and London, 1886, vol. vii. p. 114. Of. Canney and Tun- 

 stall, " Proc. Physiol. Soc.," March 1885, Journ. PhysioL, Cambridge and London, 1885, 

 vol. vi. 



