The Electrical Response of Muscle 221 



thing as the electrical response which accompanies the normal contraction 

 of skin-covered muscles in man, to say an}i;hing as to what it indicates. 

 Only if such experiuients gave positive results — e.g. if it could be demon- 

 strated that the rhj^thni obtaining in the electrical reflex response of the 

 gastrocnemius of the rabbit, which, according to Piper [(1), p. 382], has a 

 frequency of 50 per second like that of the lower-arm flexors of man, can 

 l)e deflnitely reduced in frequency by cooling any part of the central 

 nervous s^'stem while the temperature of the muscle remained constant — only 

 then should I feel inclined to admit Dr Piper's conclusion that the rhythm 

 lie has observed in his records is also that of the normal stimulus. Until 

 1 have any evidence of this sort, I cannot help thinking that the rhythmical 

 effect which both he and I have recorded in human muscles contracting to 

 the normal stimulus, partakes of the nature of the wavelets seen in m}- frog 

 records rather than of that of the waves. But before giving my reasons 

 for so thinking, I must give some account of my own experiments on such 

 muscles, in which the electrical response was recorded with the same 

 instrument or with one having the same properties as the one used for the 

 frog experiments I have just described. 



III. The Rhythm exhibited ix Capillary Electkometek Records 



OF THE ReSPOXSE OF MuSCLE TO VoLUXTARY EFFORT IX MaX. 



I have taken records of the response of the lower-arm flexors with 

 about twenty diflerent people, with some of them on more than one occasion. 

 I am indebted to about a dozen Oxford undergraduates and to a few other 

 friends (four of them women, and two of them children) for their kindness 

 in acting as subjects for these experiments. 



Methods. — As leading-ofl' electrodes I have, as a rule, used sponges 

 soaked in .salt .solution, and tied up with muslin to prevent possible altera- 

 tion of area of contact when the muscle contracted. They were applied to 

 the skin, the one over the particular part of muscle required to give its 

 record, the other to that over some other part of muscle or other tissue. 

 Outside each sponge was a zinc rod with binding screw. I have also used, 

 in certain experiments, non-polarisable electrodes similar to those used by 

 Piper, or others made by interpolating a zinc-sulphate-containing sponge 

 between the sponge which touched the skin and the zinc. There is not 

 the same necessity for using non-polari.sable electrodes with the capillary 

 electrometer as there is with the galvanometer, and therefore, when I found 

 that it made no diflerence to the result (the record) which of these three 

 kinds of electrode I emploj-ed, when trying them all in turn on the same 

 person, I felt justified in continuing to use the simplest and most con- 

 venient kind which I had used in the flrst instance. The electrodes were 

 each held in position by elastic bands, the positions being, with each person 

 to begin with, the same as tho.se cho.sen by Piper. The arm rested 

 supine on an insulating support, and in the hand was a dynamometer in 



