PRACTICAL PHASES OF MENTAL FATIGUE. 517 



long vacation brings the needed rest.* Those who train athletes 

 realize that the fatigue limit must not be passed if possible, and 

 this law is recognized as well in the training of racing horses, f One 

 who has observed his experience in learning to ride the bicycle must 

 have discovered that practice pursued when in a condition of ex- 

 haustion operates rather to retard than to promote facility. So in 

 matters of the mind activity carried to excess, which point is further 

 removed in some cases than in others, results in retardation of 

 growth, even though no more serious consequences ensue. 



II. 



As might be readily inferred, even if we were lacking xperimen- 

 tal evidence, fatigue interferes with the normal activities alike of 

 body and mind. One of the earliest and most conspicuous effects 

 may be observed by any one in the people about him a decrease in 

 the rapidity of physical action. The child depleted of nervous en- 

 ergy, for whatever reason, will usually be slower than his fellows 

 in performing the various activities of home or school. If observed 

 during gymnastic exercises it may be noticed that his execution of 

 the various commands is delayed; in responding to signals he is be- 

 hind his comrades whose nervous capital is not so largely spent. 

 And what is here said of the child is, of course, equally true in prin- 

 ciple of the adult; the effect of fatigue in his case will be revealed 

 in less lively, vivacious, and vigorous conduct in the affairs of busi- 

 ness or of society. Mosso,:}: Burgerstein,* Scripture, j| Bryan, A and 

 others have been able to confirm by scientific experiment what peo- 

 ple have thus long been conscious of in a way that cerebral fatigue 

 renders one slower, more lethargic in his activities. It seems clear, 

 to hazard an explanation, that when nerve cells become depleted 

 up to the point of fatigue Nature designs that they should be re- 

 leased from service in order that repair may take place. This 

 rhythm of action and repose seems to be common to all forms of 

 life. The phenomenon of sleep is an expression of this principle, 

 and is characterized by almost entire absence of activity. 



Again, fatigue disturbs the power of accurate and sustained 

 bodily co-ordinations, particularly of the peripheral muscles, or those 

 engaged in the control of the more delicate movements of the body, 

 as of the fingers. Every one must have had the experience that con- 

 sequent upon a period of exacting labor (physical or mental), or 



* Educational Review, op. cit. 



f Bryan, Addresses and Proceedings of the National Educational Association, 1897. 



Pedagogical Seminary, vol. ii, pp. 20 et seq. * Ibid., op. cit. 



|| The New Psychology, pp. 128-132. 



A The Development of Voluntary Motor Ability, p. 76. 



