5i8 POPULAR SCIENCE MONTHLY. 



worry, the hand becomes unsteady, as revealed in writing or other 

 fine -work, the voice is not so perfectly controlled as at other times, 

 and perhaps involuntary twitchings or tics make their appearance 

 in the face or elsewhere. Ordinarily people regard these phenom- 

 ena as evidences simply of " nervousness," but, as commonly used, 

 this term does not take account of the neural conditions responsible 

 for these abnormal manifestations. Warner * points out that nerve 

 cells in a state of fatigue become impulsive or spasmodic in their 

 action; there is not such perfect balance as usually exists between 

 them when in a normal, rested condition, and this results in lessened 

 power of inhibition. Scripture f and others have shown by experi- 

 ments in the laboratory that fatigue renders co-ordination less sus- 

 tained and accurate. If, now, one observes a group of people, young 

 or old, in which some or all have passed the fatigue limit, he can see 

 the cause of many of those occurrences which give the teacher in the 

 school, for example, continual trouble. The children will doubtless 

 be moving incessantly in their seats, books and pencils may be drop- 

 ping upon the floor, and various signals are responded to slowly and 

 :in a disorderly manner. The restlessness is probably due for the 

 most part to the effort of the pupils to relieve the tension of muscles 

 induced by overstrain, while inability to accurately co-ordinate the 

 muscles employed in holding pencils and books causes objects to slip 

 out of the pupils' hands upon the floor. One has but to observe his 

 own experience, and he will soon realize that when nervously ex- 

 hausted he is not so certain of retaining securely small objects which 

 he handles. This accounts for what is sometimes regarded as care- 

 lessness in school children as well as in adults, exhibited in slovenly 

 writing, in breaking dishes, and in similar occurrences. Any task 

 demanding delicate and sustained adjustment of the finer muscles 

 on the part of one fatigued will be liable to be performed in a care- 

 less manner, as we are apt to feel. Often more than not the term 

 carelessness probably denotes impaired neural conditions, as well 

 as consequent mental dispersion, if one may so speak, leading to 

 inaccurate and intermittent mental and physical adjustments to 

 duties in hand. 



Cowles \ observes that the first ])romincnt and serious mental 

 concomitant of nervous depletion is revealed in the inability to 

 direct the attention continuously upon any given subject; and James 

 has said tliat when one is fatigued the mind wanders in various direc- 

 tions, snatching at everything which promises relief from the object 

 of immediate attention. Experiments in the laboratory upon the 

 keenness of sense discrimination of data appealing to sight, hearing, 



* Mental Faculty, pp. 76, 77. f The New Psychology, pp. 236-248. 



X Op. cit., p. 47. 



