PHYSICO-CHE.AIICAL BASIS OF TRANSMISSION 387 



tions the wave of activation fman.cd by tlu- . i- 



ing of the metanic surface) moves slowly upward at 

 the rate of only a few centimeters per second; whUc 

 in the case of a wire completely immersed in a 

 large volume of acid the transmission is too rapid to 

 follow with the eye, i.e., some hundred cenlii |)cr 



second. 



Rapidity in the local variation of potential in nerve 

 or other conducting tissue is thus a necessary condition 

 for rapidity of transmission. The table given on page 

 328 shows a general proportionality between the rate 

 of development of the bioelectric currents in d. it 

 tissues and the rate of transmission. Tiie slowing of 

 the bioelectric variation in a particular tissue, by cold, 

 anaesthesia, or fatigue, invohcs a corresponding slowing 

 in the transmission rate. An exact proportionality is 

 hardly to be expected, because the other })roperties of 

 the tissue, especially its irritability and its electrical 

 conductivity, are also affected by the change of condi- 

 tions, and other variables enter; but that the rate of 

 electromotor variation is the chief factor determining 

 the speed of transmission seems clearly indicated by tiie 

 observations cited in the table. 



With regard to the other variable, s, the di c 



from the active-resting boundary through which the 

 local bioelectric current is effective as a stimulus, detinitc 

 information is difficult to obtain. T have att< \ 



to estimate this distance in frogs' nerve by i g 



the maximal distance between two platinum *.'. s, 



applied to the tissue and having a IM). similar lo 

 that of the bioelectric variation (20 to 40 millivolts), 

 at which stimulation occurs on the make and break of a 



