CROSS-ED UCA TION. 



591 



hand in squeezing a dynamometer develops the strength of the 

 other members of the body, will it not also develop their dexterity 

 or their advance? Again, if the development of voluntary power 

 — let us say, frankly, " will power " — in one direction brings about 

 a development in other directions, why should we limit the trans- 

 ference to muscular activity? Why can we not expect that the 

 development should be extended to the higher forms of will power 

 that go to make up character? The outlook begins to be stirring 

 on account of its vastness. If the last principle be admitted, there 

 seems no argument against the claim that some forms of manual 

 training, such as lathe work and forge work, are just the things 

 to develop moral character. By the same reasoning we would be 

 obliged to admit the often-made argument that training in Latin, 

 Greek, and mathematics furnishes a means of general mental de- 

 velopment. If we admit the principle, we find ourselves at once 

 involved in important educational controversies. However we 

 may think in respect to these questions, it is plain that it is worth 

 while to climb a ladder which has such an outlook at the top. 

 Let us begin. 



In the first place, the fact of cross-education is established. 

 Let us ask in what this education consists. On this point some 

 curious observations have been made by Prof. W. W. Davis,* 

 now of Iowa College. The subject of the experiment began by 

 raising a five-pound dumb-bell by flexing the arm at the elbow; 

 this called into play chiefly the biceps muscle for lifting and the 

 forearm muscles for grasping. This was done as many times as 

 possible with the right arm, and then, after a rest, with the left 

 arm. The subject then entered upon a practice extending from 

 two to four weeks ; this consisted in lifting the weight with the right 

 arm only. At the end both arms were tested as at the start. 



The results were strange enough. The unpracticed left arm 

 gained in power as we expected, but it also gained in size. Care- 

 ful measurements were made by Dr. J. W. Seaver, of the Yale 

 Gymnasium, on the girths of both upper arm and forearm. Let 

 us compare the gains in girth with the gains in power : 



* Studies from the Yale Psychological Laboratory, vol. vi. 



