222 THE HUMAN MOTOR 



down dead as soon as he had accomplished his mission, is often 

 quoted, and not without reason. 



Before the extreme limit of exhaustion is reached, tiring work 

 gives rise to feverishness accompanied by pains in the joints, 

 which are also of toxic origin^ 1 ) Moreover, intense labour raises 



the temperature of the body a little, from 1 to 1-5 C., and that 

 without any inconvenience. 



Age only causes insignificant modifications to the organism 

 between 20 and 50 years of age ; human strength progresses up 

 to 40, but is not marked by any physiological troubles. As has 

 been seen already ( 142) the rhythms of the respirations and the 

 pulse alone are modified. There are also differences in the two 

 sexes ; in particular, the rhythms are slightly quicker in woman 

 and the blood not quite so rich in red corpuscles. The physiolo- 

 gical state presents greater differences in the period of pregnancy, 

 the muscular power of the woman then decreasing. All fatigue 

 should then be spared her, otherwise both mother and offspring 

 will suffer. ( 2 ) 



There are also individual characteristics ; thus obese subjects 

 have blood that is less rich in red corpuscles ; the blood of 

 muscular subjects on the contrary is very rich in red corpuscles 

 (Malassez) , and they tire less quickly. Of course normal internal 

 conditions are not found in all workmen, for intemperance 

 brings troubles which predisposes them to work but feebly. It 

 is profitable to watch over their health, and to do what is neces- 

 sary to protect it, in spite of themselves. 



158. Influence of the Senses. The role of the senses is obvious, 

 notably that of sight, of hearing, and of touch. They can be 

 developed and rendered more useful. 



Good sight contributes to the perfection of work. Workmen 

 have not all got the same eyesight ; therefore the short-sighted 

 should not work without glasses, because they stoop to see better, 

 what they are doing, and are fatigued by that defective attitude. 

 Sight permits a better equilibrium of the body. 



In certain trades painters, dyers, decorators, etc. the work- 

 man must be able to distinguish colours, and this often needs 

 education. " Daltonism " (colour blindness) is the inability to 

 distinguish between red, yellow and green. About 4% of men 

 are Daltonists, but women very seldom. 



Hearing assists the workman in his normal conduct in the same 

 way that it gives the note to the singer ; thus it assists the 

 periodic action of the tools, as smiths swing their hammers to a 



f 1 ) A. Mosso (Arch. Ital. Biol., 1890, vol. xiii., p. 165). 

 () RenS Laufer (Nouvelle Revue, 1907, p. 11). 



