1903.] Nervous Impulse in Tall- and Short Individuals. 417 



In order to keep a check on the experiments, these were made in 

 two pairs (except in subject AB), two contractions of " near " excita- 

 tion and two of "far" being superposed, any accidental error of any 

 one contraction could be thus detected by the non-congruence of the 

 curves. 



It was found possible to obtain with care four or five consecutive 

 experiments on the same subject without error in any one case greater 

 than O'OOOl second from the recording apparatus (fig. 2). 



The reading of the time difference between the " near " and " far " 

 curves presents some difficulty owing to the gradual rise of the lever 

 at the commencement of the curve. In order to check my own 

 readings, I asked Dr. T. G. Brodie to re-measure several of my curves, 

 and his independent readings have agreed with mine within the limit 

 of error of O0001 second. 



Experiments. 



The results on the human subject agree with those obtained from 

 the frog, namely, that per unit length, the rate of the nervous impulse 

 is the same in all individuals examined, and the consequence follows 

 that the time taken to traverse the limb nerves in a tall man is 

 appreciably longer than in a short man. In the subjects examined, 

 this difference was O'OOl second approximately, and if the reaction 

 time to touch from the hand or foot were measured, this would 

 cu-trris paribiis be from 0'003 0-004 second longer in the taller 

 individuals, a distinct penalty to pay for their greater stature. 



It will be observed that the mean velocity, deduced from the total 

 number of forty experiments, is 66'8 metres per second (0'1), a 

 figure that is rather higher than that originally given by Helmholtz* 

 and more recently by Waller, t 



* Helmholtz u. Baxt, ' Monatsb. d. Berl Ak 1867 s. 228 (1870, s. 184). 

 t Waller, loc. cit. 



