INDUSTRIAL LABOUR 



451 



seconds 



Of 2 3 4 5 6 7 d 9 W 11 ,2 /J .. /J / // / 



FIG. 308. 

 Respiratory curves of an orator. 



most intense intellectual work gave rise to any expenditure of 

 energy measurable in calories. Thus when a scientist was 

 enclosed for three days in a calorimetric chamber while engaged 

 in heavy intellectual work (the study of a German treatise on 

 physics), no appreciable increase in the static expendituie could 

 be observed, f 1 ) Nevertheless we know that mental activity has 

 definite physical and physiological effects ( 149). It diminishes 

 muscular power, produces toxic substances in the organism and 

 causes general fatigue. If continued for long periods, ten hours 

 or more, the circulation is retarded, the properties of the nervous 

 matter are modified, the reaction to external stimuli decreases, 

 the personal equation increases, and the senses, in general, become 

 less alert. 



Although the expenditure of energy in intellectual work cannot 

 be measured as that expended in muscular labour, yet it is certain 

 that as far as fatigue is concerned the difference is one of degree, 

 not of kind. Hence, in all intellectual occupations, a considera- 

 tion of the fatigue involved must not be neglected. 



Mental activity, as muscular exertion, can be organised and 

 directed. Great intellectual power is often dissipated uselessly 

 by confused and unsystematic methods of thought. This is 

 generally the result, of unscientific training and the failure to 

 acquire the habit of reasoning logically. The delicate mechanism 

 of the brain must not be overstrained. Such matters, however, 

 belong to the domain of psycho-physiology. 



341. Food and Occupation. Since the expenditure of muscular 

 and nervous energy differs in various occupations, it would be 

 reasonable that the nourishment provided for the body should 

 be arranged with due regard to the exertion which it is called to 

 undergo. Certain investigations have been made on this subject. 



( x ) Bulletin, Nos. 44 and 136 (1897 and 1903). 



