226 ' Buchanan 



other individual I luive so far tried, and this was true on each of three 

 separate occasions. Siuiihir records have since been obtained with one other 

 person (see Addendum). All the experiments in which the position of the 

 leading-ott" electrodes was altered were made upon him also. When most 

 regular the frequency was slower than it is in most people, and each 

 individual etiect was stronger. The strength of the mechanical effect 

 was not in any way remarkable (see p. 227). 



When both electrodes were small the ascents as well as the descents of 

 the separate excursions were less steep, i.e. the effects, as Piper has shown, 

 are weaker. I attribute the difficulty I had experienced until lately in 

 recording the electrical response of voluntary muscle in man to the fact 

 that I had previousl}' tried to obtain it by leading off from surfaces too 

 small for such negativity as might prevail under them to be able to affect 

 the electrometer. 



(b) The recording muscle. — Besides the muscles in the lower arm, I 

 have used those in the hand and those in the jaw. In the hand muscles 

 a response frequency of 100 to 140 per second appears more often than 

 any slower one. Records taken with the masseters show a series of 

 very fine teeth the frequency of which is more uniform than it usually 

 is in records obtained from the arm muscles. It is always high, 

 frequencies of 170 to 180 or even 200 per second being met with. 

 I shall have to refer again to the difference of frequency obtaining in 

 different muscles (p. 237). 



With one subject an attempt was made to alter the temperature of 

 the fibres, and records were taken when the recording arm was now at 

 room temperature (13^ C), now in an incubator kept at 35° C. Although 

 the records were good they exhibit the usual irregularity, so that I 

 should hesitate to draw any conclusions from them. I hope to repeat the 

 experiment with the subject who gave the fig. 5 records. 



(c) The voluntary effort. — With each person records were taken 

 when he was grasping as hard as he could, and the dynamometer scale 

 was read. With some people records were also taken when they were 

 purposely not exerting their full strength, but such as to make the scale 

 read about half or two-thirds of their maximum. The difference in the 

 strength of the effect, i.e. in the steepness of the ascents and descents of the 

 undulations on the curve, was very marked in any two such records taken 

 with the same person, just as the difference of amplitude of the swings of the 

 fibre of the string-galvanometer was marked in Piper's records. The whole 

 response was, however, of the same type, i.e. the outline of the curve was 

 equally irregular in the two cases with most people; and it was just as 

 regular when the contraction was weaker as when it was strong in the flexors 

 of the individual with whom the fig. 5 records were taken, although the 

 jags were sometimes so small that they were difficult to count. To ascertain 

 whether or not the frequency of the rhythm varies with the strength of 

 the effect, the records obtained with this individual are the most useful. 



