The Electrical Response of Muscle 213 



have been produced. It has, as a matter of fact, been shown both by 

 Garten (6) and by myself (4) that a rhythm of a frequency of from 50 

 to 100 per second may be observed in the electiical response of excised 

 frog's muscle when either it or its motor nerve is subjected to a continuous 

 stimulus (whether actually so, or consisting of instantaneous stimuli recurring 

 in such rapid succession that the whole may be so regarded) or to a variety 

 of other stimuli of short duration which have notliing discontinuous in 

 their nature. The frequency of this rhythm varies (as we have each of us 

 shown) with the condition of the muscle much more than with the 

 particular nature of the exciting stimulus. The central stimulus which 

 provokes a normal contraction in any animal might just as well partake 

 of the nature of any of these non-discontinuous stimuli as of that of the 

 particular discontinuous one which Piper found to produce an effect on 

 his galvanometer of a similar character. I had, indeed, laid stress on the 

 fact [(4), p. 149] that the central stimulus intervening in the reflex 

 response of the muscle of a frog in certain stages of strychnine poisoning is 

 not to be regarded as of the nature of a series of in.stantaneous stimuli, 

 although its effect on the muscle can be imitated (as in photo. 35, on pi. vii.) 

 by that of a series of such stimuli, recurring with a frequency of, say, 50 

 per second, interrupted at intervals. The view then expressed was after- 

 wards put to the test and conlirmed. The experiments which confirm it 

 deserve more than the passing mention they received in the following year. 

 (5), and since the results obtained have so distinct a bearing on tlie subject 

 to be chiefly discussed in the present paper, namely, on the significance to 

 be attached to the rhythm observed in the electrical response of a muscle in 

 voluntary contraction, I propose to begin by giving some account of them 

 and to reproduce a few typical records. 



II. The Two Kinds of Rhyth.m exhibited in the Reflex 

 Hlei TKicAL Responses of Fro(;'s Muscle in Strychnine Spasm. 



For the .sake of clearness I shall henceforward designate J:hose undula- 

 tions which occur in the records with a frequency of from 40 to 100 per 

 second as wavelets, the curves recurring with a fretpency of from 8 to 14 

 per second (on which the wavelets may be superimposed) as waves. 



The independence of waves and wavelets is shown by the fact that 

 either may be present without the other. I ha\e already reproduced 

 records of frog's muscle in strychnine spasm showing (a) wavelets exclu- 

 sively or almo.st exclusively [(4), pi. vii., ph. 37: })!. ix.. ph. 45, 46, 47); 

 (b) waves exclusively [(4), pi. viii.. ph. 31), 40, 41 : })1. ix.. ph. 50] : and (c) 

 the two side by side [(4), pi. vii.. ph. 3S : pi. ix.. ph. 4S, 4i>]. The records I 

 have now to reproduce are to bear witness to what was stated in 1902, namely, 

 that what I now call wavelets depend for their frecjuency upon something 

 in the muscle, that the waves depend for theirs upon something in the 

 spinal cord. 



