The Electrical Response of Muscle 235 



strychnine spasm. Granting for the moment that a series of Zeitreize are 

 coming from the cord, their frequency would only manifest itself in the 

 records if the interval between one Zeitreiz and the next was so long that 

 the effect of the first was over before that of the next began. It very 

 frequently becomes so, or can be made to become so, in the strychnine frog, 

 and then the rhythm of from 3 to 14 per second, already described, mani- 

 fests itself in the records, with the quicker rhythm of 40 to 120 per second 

 superimposed upon it. On the other hand, I am not at all sure that it is 

 true that we have no evidence of a slower rhythm as well as of one vary- 

 ing between 40 and 120 per second, in the lower-arm flexors of man 

 contracting at will. Many of my records show, as I have said (p. 223), a 

 grouping of the undulations on the curve, the groups occurring with a 

 frequency of from 14 to 30 per second. The beginning of such a group is 

 always a particularly steep ascent, which means a particularly strong 

 variation, such as I have shown (1901) to be frequently present at the 

 beginning of each wave in the strychnine spasm record of the frog. 



(ii.) Piper's second objection to my view is that, " keeping to physio- 

 logical conditions of experiment " (by which, I suppose, he means avoiding 

 the use of drugs such as strychnine) a muscle never responds with 

 rhythmical oscillations to a single stimulus. This is true perhaps with 

 most muscles, if the single stimulus is instantaneous. But, as I have 

 recently shown [(10), fig. 2], even to a single instantaneous stimulus the 

 gastrocnemius of the frog may give more than one oscillation in the record 

 of the electrical response ; and it and other muscles certainly do so when 

 excited by break ascending galvanic currents [(4), pi. vii., ph. 33, 34]. 

 Moreover, with a stimulus of somewhat more appreciable duration, such as 

 that given by Garten's guillotine [(6), p. 340], oscillations seem always to 

 occur. So far as I am aware, no records have been taken with a quick 

 capillary electrometer of the response of muscle excited by v. Kries's 

 Federrheonom (7), and the oscillations in cjuestion are far too <|uick to 

 be observed by the eye. 



The view which I am now upholding, that the rhythm of the electrical 

 response accompanying voluntary contraction is mainly of peripheral 

 origin, is that of Wedensky [(11), p. 260]. I was unable to accept it in 

 15)01 [(4), p. 152], partly because I had then no records of the voluntary 

 response to compare with my records obtained with frog muscles, and 

 partly because I was not always able to follow, as I then said (p. 139), 

 his descriptions of the sounds he heard with the telephone. 



The fact that the frequency is not altered by the strength of 

 the central stimulus provoking it — a fact insisted upon by Piper and 

 not contradicted by anything in my records — seems to me, as far as it goes, 

 to furnish evidence in favour of this view, or rather against the view that 

 the response f)-e(]uency represents the innervation frecjuency. I have already 

 shown [(4), p. 135] that when artificial stimuli of a frequencj^ capable of 

 impressing itself upon the muscle, are applied to the nerve of the frog's 



