32 Thaddeus L. Bolton and Eleonora T. Miller 



record as had been obtained from the right. As both hands had 

 reached the limit that could be recorded on the apparatus, it is 

 difficult to tell what would have been the relative standing had 

 the experiment been continued further. 



With B. the right hand maintained its supremacy until the 

 suspension of exercise with it was caused by a broken mask and 

 injury to the hand. After exercise was taken up in the fourth 

 series it never again quite succeeded in equaling the left hand. 



Further comparisons of right and left hands for both reagents 

 must be made on the basis of height of contraction. M. found 

 the movement of the left hand always easier than that of the 

 right. During the first three periods of work, however, the right 

 hand made a higher average contraction than the left. During 

 the fourth period the left hand gained considerably in the height 

 of contraction, surpassing the right, but lost in the number of 

 contractions. If our interpretation that the height of contraction 

 represents perfection of coordination in movement be correct, 

 then the left hand grew continuously in this respect. But as a 

 highly coordinated movement is more fatiguing than a less 

 highly coordinated one, we might expect that there would be 

 some loss in endurance, which is shown by a reduction in the 

 number of contractions. In case of B. the right hand was supe- 

 rior to the left in all respects except in number of contractions 

 and maintained its superiority until work had to be given up. 

 The left hand, however, grew very slowly in height of contrac- 

 tion, even to the end of the fourth period of work. The enor- 

 mous practice gain which it made was due almost entirely to 

 increase in power of endurance and rhythm of movement. The 

 increase in number of contractions began during the third period 

 of work and the number continued to grow up to the end of the 

 fourth period. Here we have again a certain compensation. 

 The hand lacked perfection of coordination, but it more than 

 made up in endurance. The movement was always attended 

 with more or less difficulty and never seemed to be easily or 

 gracefully performed. This is further evidence that a highly 

 coordinated movement is expensive of energy, although it may 

 be proportionately more effective in the accomplishment of work. 



no 



