VELOCITY OF TRANSMITTED IMPULSE 143 



a tissue which was slightly sluggish. The distance of the 

 point of application of stimulus — namely, 20 mm. — was 

 maintained constant, the intensity being varied in the 

 successive experiments. The vibrating recorder had a 

 frequency of 10 per second. The lowest record is the 

 result of a stimulus-intensity of '5. The total time of 

 transmission is seen to have been 2"i seconds. The true 

 time is obtained by subtracting from this the latent period, 

 the average value of which is found to be about "i second. 

 No appreciable error will be introduced in practice by 

 adopting this average value for the latent period, for its 



Fig. 85. — Effect of intensity of stimulus and its after-effect on velocity. 

 Lowest record under stimulus -5 ; the next under stimulus 4. Velocity 

 increased under stronger stimulus. Enhancement of conductivity by 

 previous stimulation seen in two upper records under -5 and 4 respec- 

 tively. Velocity high and practically the same in both cases. 



variations are very slight, being of the order of hundredths 

 of a second. The actual time here taken for transmission 

 is thus 2 seconds, with a stimulus-intensity of "5. 



The record next above gives the result when the stimulus 

 intensity was 4, that is to say, increased to eight times 

 its original value. The total time is now found to be 

 decreased to i*6 second, the true time after deducting the 

 latent period being thus 1*5 second. The velocity under 

 this increasing intensity is thus enhanced in the proportion 

 of 2 : 1 "5, or 33 per cent. To find out if there had been 

 any after-effect of stimulation, a record was once more 



