The Elect i-ical Response of Muscle 223 



(see tiu-. 8, p. 219) or in frog's muscle made to give a persistent contraction 

 by the application of a descending constant current to the motor nerve, by- 

 breaking an ascending constant current running through the nerve, or by the 

 stimulation of either the nerve or the muscle itself by a series of instan- 

 taneous stimuli following one another in such quick succession that they 

 are unable each individually to produce a distinct effect. So great is the 

 irregularity of the excursions in the records obtained with these arm 

 muscles in most people, that it is very difficult to say what their frequency 

 is. One frequency ma}- prevail for a few hundredths of a second, then 

 another, then the first back again, or yet another. In most of the records 

 a frequency of 100 to 120 per second manifests itself somewhere, also one of 

 about 60 to 80 per second. It was only very rarely that one as low as 50 per 

 second also appeared, only, in fact, in four of all the people with whom I 

 have so far taken records ; in one of whom, however, it even at times became 

 as low as 40 per second (see table on p. 227). The effect, although it varies 

 greatly in different people, does not, so far as my present experience goes, 

 seem to be altered in any definite way either hy sex or hy age. The jags 

 on the curve are often — and in the records taken with some people more 

 than in those taken with others — thrown into groups which recur with a 

 frequency of from 14 to 30 per second, but the curve outline is so 

 irregular that I can lay but little stress upon the presence of these groupings. 

 It may, however, be worth mentioning that groupings of the same sort of 

 frequenc}^ occur in records taken with the masseters, where, as we shall 

 presently see, the excursions which fall into groups have a much greater 

 and more constant frequency than thej' have in the arm muscles. 



In the hope of getting more information as to what it was tluit my 

 records represented, I have, with one or more of the subjects, attempted to 

 alter the effect by \arying certain conditions. 



(a) The contacts. — The connections with the electrometer were 

 usually such that the part of the flexors which became most tense when 

 the fist was clenched was connected with the acid. The first excursion 

 which the meniscus made from its resting position was then alwaj's 

 adostial (upwards in the records), not only when the second electrode 

 was distal to it, as it usuall}- was, but also when it was on the elbow or on 

 the shoulder. Thus the spot chosen as being mechanicall}- the most active 

 one always becomes galvanometrically negative before any other spot, 

 whether or not these also become negative afterwards. When the connec- 

 tions with the electrometer were reversed the first movement was alwa3\s 

 abostial. This is, of course, only what was to be expected on the assump- 

 tion that what we are recording is essential!}- a muscular phenomenon, and 

 the fact therefore helps to support the assumption. The records give 

 however, as a rule, little, if any, evidence of the way in which the con- 

 nections had been made except at the start, so that unless this appears on 

 the plate I doubt whetiier anyone could tell with confidence from the 

 records which way the connections had been made. 



