652 POPULAR SCIENCE MONTHLY. 



the point so often in a state of fatigue as when rested, but the 

 strain seems much greater upon the whole body, causing twitch- 

 ing and other choreic movements if continued very long. This 

 evidence all points to the fact that mental activity expends 

 nervous energy which is revealed in lessened muscular control. 

 So in the direct mental tests, a pupil can not after a half day's 

 work in school do such an apparently simple thing as to divide a 

 line into a given number of equal parts with the accuracy that he 

 can earlier in the day. The same effects of fatigue are evident 

 in the lessened power of retention of visual images, and of identi- 

 fication of similar impressions. In short, fatigue lessens mental 

 ability; produces, relatively speaking, dullness, stupidity, and 

 inaccuracy in thinking. 



Substantially these same results have been reached in experi- 

 ments made by Professors Burgerstein,* of Vienna, and Kraeplin,f 

 of Leipsic, and at Leland Stanford Junior University X in our 

 own country. Mr. Galton * has secured statements from adults 

 to the effect that a hard day's work lessened the keenness and 

 trustworthiness of their intellectual operations. They could not 

 perceive so accurately, remember so readily, or reason so effi- 

 ciently. Mr. Sinclair, || in his studies of schoolroom fatigue, has 

 obtained similar data. 



The statement was made in a previous paragraph that people 

 differ greatly in the readiness with which fatigue ensues upon 

 mental effort. The nerve cells seem to be so constituted in some 

 people that they give off an undue amount of energy upon slight 

 stimulus.'^ This fact may be easily observed in a group of chil- 

 dren as well as among adults. A slight noise, a touch upon the 

 shoulder, or a sharp question will cause some to react with an 

 amount of vigor quite out of proportion to the degree of the 

 stimulus. The body will twitch, the face flush, and the thought 

 will be confused. Other children will show none of this excessive 

 display of energy. Their reaction is proportionate to the stimu- 

 lus, and in this way they save their energies. Consequently, other 

 things being equal, they endure much longer and can undertake 

 more difficult and trying ordeals without fatigue. Again, it is 

 easy to see when any number of children are gathered together 

 that some have much more energy always at their disposal than 

 others. In other words, they are better nourished, which means 

 in this connection that they have more nerve energy that may be 

 employed in either mental or physical work. The important 



* See Kraeplin, op. cit. \ Op. ciC. ^ Pedagogical Seminary, vol. iii, p. 213 et seq. 



* Op. cit. 1 Op. cit. 



^ Cf. Bryan. The Development of Voluntary Motor Ability. Proceedings of the De- 

 partment of Superintendence of the N. E. A., 1897. 



