MOTOR COORDINATIONS. 147 



serious, since we had to use a large current in the primary (1 ampere), 

 and even then the muscle threshold at skin resistance was usually found 

 with the primary and secondary coils so close together that a change 

 of a single millimeter made relatively large changes in the intensity of 

 the induced current. On these grounds we feel doubtful if the fingers, 

 in spite of their mobility, are adapted to serve as indicators of muscle 

 threshold to Faradic stimulation by the Martin method. A second 

 difficulty arose out of the required intensity of the current for threshold 

 stimulation. On account of the possible variations of skin and elec- 

 trode resistance, we felt that only /3 values could be regarded as signifi- 

 cant in these measurements. But on account of the intensity of the 

 current demanded, we found it impracticable to get more than one 

 threshold with known resistance, in addition to the threshold at skin 

 resistance, and this one additional threshold was obtained with the 

 secondary coil at a relatively unreliable part of the scale. The data 

 at hand show no clear tendency of muscle threshold after alcohol, 

 but, as we have indicated, they are too unreliable to be of any real 

 significance. 



(2) On the problem of muscle fatigue and recuperation we have no 

 direct data. Prolonged free oscillation of the finger, which we proposed 

 in the program to study in this connection, proved to be complicated by 

 too many capricious factors to be usable. Preliminary records clearly 

 showed that some subjects unconsciously saved themselves at the 

 beginning for the long process. Moreover, they yielded variously to 

 growing discomfort, fatigue, etc. In our experimental series we con- 

 tinued to use the free oscillation of the finger, but only for the initial spurt 

 and in quite another connection. Incidental indications of fatigue from 

 these records will be discussed in the latter part of this chapter. 



(3) Attempts to measure muscle-tremors were made by attaching 

 delicate photographic recorders to the finger, wrist, and forearm respec- 

 tively, with adequate supports for the member that was not under 

 observation. The instrumental technique was accurate. A long lever 

 was placed before a photographic recording-camera in such a position 

 that a shadow of its free end fell across the slit. The limb whose 

 tremors were to be measured was then attached to the lever by a light 

 but rigid connector in such a way that the tremors were magnified ten 

 times. But with this frictionless recording technique the result of the 

 preliminary records gave such wide variations within a few seconds of 

 each other under supposedly normal conditions that we decided to drop 

 the measurements until the sources of variation could be investigated. 



(4) The speed of movement developed under our analysis of its con- 

 ditions to a more significant measurement than we had at first ventured 

 to expect. It takes its proper place with respect to the rest of the 

 neuro-muscular processes only when we regard it as an indicator of 

 primary motor coordination. 



