PHYSIOLOGICAL EFFECTS OF LABOUR 213 



The excitability of the nervous centres is then lessened, and they 

 show increasing inertia. It is thus that thought has more lorce 

 in the morning than in the evening, f 1 ) The sensitiveness of the 

 skin has been measuied by means of the esthesio meter, and it was 

 found, with school children, that it diminished progressively in 

 the course of the day's studies ( 2 ) or after prolonged mediation 

 ( 249). Whilst the liminal distance is 3-5 millimetres on the 

 lower lip on the days of study, it is only 1 on Sunday, the day of 

 repose. In young workmen (apprentices) the difference, on the 

 contrary, is hardly appreciable. Finally, account must be taken 

 of attention and reflexion which bring into play various muscles 

 of the face, and the sustained contraction of which is a cause of 

 fatigue. It can be stated, without presumption, that these 

 muscular contractions have led several experimentalists astray 

 who observed a rise of cerebral tempera tuie (Mosso, Gley) or more 

 active exchanges of gas when the nervous centres were either 

 excited normally ( 3 ) or by an absorption of liquids, such as 

 absinthe, which provoke epileptic fits.( 4 ) Whatever may be its 

 nature nervous fatigue is real and shows itself in proportion to the 

 degree of attention demanded. Thus work which makes demands 

 on the intelligence is certainly more onerous than operations 

 which can be effected automatically. The intervention of 

 thought is not a factor of economy in the human organism. 



Cerebral fatigue diminishes not only the tactile sensibility, 

 but also the general sensibility ; the personal equation increases 

 and the aptitude for work weakens. It is good to vary occupa- 

 tions, so that the same nervous centres are not constantly called 

 upon. The endeavour should be made to vary the occupations 

 of the woikman, and his leisure should be spent in pursuits which 

 call forth different thoughts and feelings from those which his 

 daily work brings to him. The weekly day of rest, which, through 

 the ages, the Divine will has laid down as a sovereign physiological 

 law, gives the needed opportunity for rest and recuperation, and 

 is a check to the avarice of the employer. Thus the re-establish- 

 ment of nervous and muscular energy results from IP- ose. Too 

 long an interruption produces a real need for activity, to which 

 the return should be progressive. But, after a rest of 24 hours, 

 a man can rapidly get into action again, unless bad use has 

 been made of the holiday. 



To sum up, fatigue is of a unique nature, being principally an 

 intoxication : " The greatest pleasure that I have experienced 



(*) A. Mosso, Les Exercises Physiques et le Developpement Intellectuel, 

 trans. Jaquet, 1904 ; Binet et Henri, La Fatigue Intellectuelle. 



( 2 ) Griessbach, Energetik und Hyg. d. N erven- Systems in die Schule, Leipzig, 

 1895 ; R. Abelson, " Mental Fatigue " (These de 1'Univ. de Rennes, 1909). 



( a ) Becker and Olsen (Die Umschau, No. 19, 1912). 



(*) Hill and Nabarro (Journal of Physiology, vol. xviii., p. 218, 1895). 



