Validity of Ergo graph as Measurer of Work Capacity 29 



the first five records, after the work was resumed in the fourth 

 ^period the average was 1735.6. The averages for the records 

 taken at the same time with the left hand are, second period, 

 1243.2 mm. ; fourth period, 1777.6 mm. The gain for the right 

 hand is 133.2 mm. and for the left hand 534.4 mm. It is evident 

 then that while the right hand shows considerable practice gain, 

 it does not approach the gain made by the left hand during the 

 same period. The right hand, however, was lower than the left, 

 and during the remainder of the experiment it did not succeed 

 more than twice in equaling the performances of the left. The 

 •averages for all records during the fourth period for the two 

 hands are, right, 1920 mm. ; left, 2019 mm. 



It is a question here of the effect of vicarious practice. Dur- 

 ing the long interval in which the right hand of B. did not work, 

 it made a clear gain of 133.2 mm. It had, however, lost in 

 habituation ; several records, one on May 19 and one on May 

 20, are manifestly below the normal, and the protocol shows that 

 the hand suffered more or less muscle soreness after work was 

 resumed. It is clearly evident that, in so far as lack of inure- 

 ment is due to local conditions in the muscle, there can be no 

 vicarious practice effect. The growth in the perfection of coor- 

 dination and rhythmical execution in one hand may possibly be 

 affected by practice of the other. If endurance is dependent upon 

 changes in the conditions of the cortical centers of the brain, it, 

 too, may be affected by vicarious practice. But it would seem 

 probable that a movement which is perfectly coordinated and 

 rhythmical-controlled would depend quite largely for its control 

 upon the lower nervous centers, and that those on the one side 

 act more or less independently of those on the other side. If, 

 then, there be such a thing as vicarious effect, it must take the 

 direction largely of coordination and rhythm. 



Certain experiments were made to test the question of vica- 

 rious practice. They were made in May and June, 1901. The 

 right hand of B. and the left hand of M. wrote five records 

 apiece, then the left hand of B. and the right hand of M. were 

 made to write two or three records a day for nine days, after 

 which the right hand of B. and the left hand of M. again wrote 

 five records apiece. These records are contained in the following 



107 



