590 POPULAH SCIENCE MOSTHLY. 



82, 79, 78, and 88 per cent. On the last day the left hand, which 

 had not been practiced in the meantime, was again tried, with a 

 success of seventy-six per cent. 



These last experiments remind us of certain familiar phenom- 

 ena. It has frequently been noticed that persons taught to write 

 with the right hand become able to write backward, but not for- 

 ward, with the left hand. This is the so-called " mirror writing," 

 which appears correct if seen in a mirror. The first published 

 observation of this fact exists in a letter from H. F. Weber to 

 Fechner, the founder of experimental psychology. Fechner, more- 

 over, noticed that with the left hand he could make the figure 9 

 backward better than in the regular way. 



Curiously enough, the principle of cross-education has been put 

 to practical use. A letter (with permission to publish) has been 

 received from Oscar Raif, Professor of Music i-n the Berlin Hoch- 

 schule : 



" In the spring of 1898 I made an experiment with twenty of 

 my pupils. I began by taking the average speed of each hand with 

 the metronome. The average of the right hand was J = 116 

 ( = four times 116 in the minute) [464 beats], and for the left 

 hand 112 [448 beats]. I gave them exercises for the right hand 

 only (finger exercises, scales, and broken accords) to develop rapid- 

 ity. After one week the average of the right hand was 120 [480] ; 

 after two weeks, 126 [604]; three weeks, 132 [528], etc. After 

 two months the right hand yielded 176 [604]. Then I had them 

 try the left hand, which averaged 152 [608], whereas in i^ovember 

 the average was only 112 [448]. In two months' time, absolutely 

 without practice, the left hand had risen from 112 [448] to 152 

 I 608]. A few of my pupils had some difficulty in playing the scales 

 in parallel motion, but were able to play them in contrary motion. 



" The tenor of my work is that in piano playing the chief re- 

 quirement is not that each single finger should move rapidly, but 

 that each movement should come at exactly the right time, and 

 we do not work only to get limber fingers, but, more than that, to 

 get perfect control over each finger. The source of what in Ger- 

 man is called Fingerferiiglceit is the center of our nervous system — 

 the brain." 



These facts, however, require further investigation, for it is 

 evident that we must begin with the fact of cross-education and pro- 

 ceed to more complicated cases. Indeed, cross-education has shown 

 itself to be one step of a ladder up which we must climb even if 

 there were no other motive except that of curiosity as to what we 

 could find at the top. If practice of one hand educates the other 

 hand, will it not also educate the foot? Again, if practice of one 



\ 



