212 Buchanan 



Thixking that the action currents of human muscle in voluntarj^ contrac- 

 tion might throw light upon the nature of the normal stimulus to skeletal 

 muscle, I had several times made the attempt to record such action currents 

 with the capillary electrometer, but had not succeeded in doing so until 

 August of last year. As the records did not seem to me to giv^e the 

 required information, I was meaning to content myself with merely 

 drawing attention to the fact that they can be obtained, when there 

 appeared a paper by Dr Piper of Kiel (1) in which were reproduced a 

 number of records of human muscle in voluntary contraction, taken with 

 the string-galvanometer, which seemed to him to give the solution to the 

 problem. 



Electrophj^siology is so much beset with the difficulty of culling, from 

 the instrumental effects observed, the underlying physiological phenomena, 

 and of excluding everj^thing for which the recording instrument alone may 

 be responsible, that the observation of the same phenomenon with different 

 recording instruinents is always likely to be of value. It is the more so 

 when, as apparently' in this instance, the records do not show the same 

 thing, and when the conclusions drawn from them by two observers are 

 diametrically opposed. 



Dr Piper's kindness in informing me of results contained in his two 

 later papers (2), (3), before their publication, and his readiness to let me 

 examine several of his still unpublished records there referred to, make 

 me feel sure that he is as anxious as I am myself to come to a true under- 

 standing of the physiological significance of what we are both recording, 

 and that he will prefer a criticism of his views to undisputed acquiescence 

 in them. I trust, therefore, that he will not take amiss any criticism which 

 appears in the following pages. 



He has recorded, with different patterns of Einthoven's string-galvano- 

 meter, the electrical responses of several different muscles in man to their 

 normal stimulus. He finds in each record one particularly prominent 

 rhythm (see note on p. 241) which he regards as constant for each muscle 

 or group of muscles. This rhythm, he thinks, indicates the rate at which 

 successive stimuli are sent to the muscle from the central nervous system. 

 He concludes, for instance, that the flexor muscles in the lower arm, which 

 are the muscles which both he and I have investigated most, are normally 

 supplied by impulses arriving with a frequency of 47 to 50 per second (1), 

 (2). He bases his conclusion — to a large extent — on the fact that the 

 galvanometer record obtained from the same muscle, when the median nerve 

 is artificially stimulated by induction shocks of about this frequency, has a 

 similar character. As will presently appear (pp. 228 and 241), the records 

 given by my electrometer of the responses of the same muscle under the same 

 two conditions exhibit very little resemblance to one another ; but even were 

 it much stronger than it is, and in the records of both instruments, the fact 

 that an effect can be imitated in one pai-ticular way affords, of course, 

 no evidence whatever that there is no other wav in whicli the effect may 



