1895.J On the Analysis of Voluntary Muscular Movements. 477 



VII. " On the Analysis of Voluntary Muscular Movements by 

 certain new Instruments." By WILLIAM R. JACK, M.D., 

 B.Sc. Communicated by Professor J. G. McKENDRlCK, 

 F.R.S. Received January 25, 1895. 



(From the Physiological Laboratory of the University of Glasgow.) 

 (Abstract.) 



The object of this investigation was to determine the greatest 

 speed of which the voluntary muscular movements were capable, and 

 how far the speed was influenced by age and education. It was de- 

 cided to limit the research to a study of the movements of the fingers* 

 as being the easiest parts to examine of the muscular system. The 

 writer has to acknowledge his indebtedness to Professor McKendrick 

 for much valuable assistance and advice. 



The first instrument used was one devised by Professor McKendrick,. 

 and figured at p. 78 of his ' Life in Motion ' (first edition, 1892). It 

 consisted essentially in a tuning fork, carrying a smoked microscopic 

 slide, and set in motion by a bichromate cell. With all its loads, 

 the fork made 117 double vibrations per second, as determined by the 

 chronograph. Lines drawn upon the attached slide perpendicular to 

 the plane of vibration were, therefore, thrown into waves, each of 

 which represented the space passed over in 1"/117. The different 

 movements investigated in this way were the following: (1.) The 

 greatest velocity attainable by the single contraction of one finger, 

 to which a finely-pointed needle was affixed. (2.) The greatest 

 velocity attainable by the single contraction of the fingers in com- 

 bined action. For this purpose the needle was fixed in a penholder, 

 and held like a pen, care being taken to see that there was no move- 

 ment of the wrist, but only of the fingers. (3.) The greatest velocity 

 obtainable in ordinary writing. In this way, therefore, the velocities 

 of a series of movements increasing in complexity could be com- 

 pared. The velocity of curves and of curvilinear figures was alsa 

 compared with that of straight lines. 



Twenty-three normal and two pathological cases were examined.. 

 The normal cases were divided into three classes : those of special 

 manual education (musicians), those of average manual education 

 (the ordinary educated classes), and those of inferior manual educa- 

 tion (working men), in whom the hands were accustomed only to 

 coarse movements, and the fingers had no special training. Of the- 

 first class there were five examples ; of the second and of the third, 

 nine. The ages varied from 18 to 62. 



While the tracings were being made the hand rested on a little 

 table at the height of the recording slide. It was found that the- 



