242 



THE HUMAN MOTOR 



It is easily seen that the thermogenesis has increased with the 

 fall of the temperature and also with the increase of wind velocity. 

 The increase in question is, all tilings being equal, less for a man 

 clothed (rather lightly) than naked (ratio A). This demonstrates 

 the protective role of clothing. The protection is all the greater 

 the colder the current (ratio B). The co-efficient of utility is 

 1-54 at 9, 1-61 at 5, ana 1-84 at 4, the speed being practically 

 constant (3-8 to 4 metres). 



The first ot these results protection against the effects of wind 

 velocity is explained by the fact that the air buries itself better 

 in the garments and forms there a non-conducting mattress. 

 The second the increasing protection with cold is because 

 cold air is a worse conductor than hot air. 



The increase of the calorific expenditure, with theincrease of the 

 speed of the current of air, corresponds to the work of the latter 

 on the body of the subject, a work which rises to 10,000 or 12,000 

 kilogramme tres per hour, about 30 Calories (for V 3 to 4 metres 

 per second), and also to the convection. 



At great altitudes and in the open air, the calorific expenditure 

 is therefore clearly higher than in the case of indoor town life, in 

 office or workshop. 



177. For a constant speed of 3-50 to 4 metres, the increase of 

 the expenditure with temperature is shown in fig. 145. The 

 curves are for a male adult subject. 



15 20 



Fio. 145. 



These quantities represent the loss by transmission or the 

 total calorific expenditure. In an environment of 20 C. the loss 

 per diem is 97 x 24 = 2,328 Calories. The average loss in the 

 radiation and convection being 1,500 Calories, there remains 828 

 Calories for the minimum physiological expenditure ( 166) ; 

 this expenditure is therefore nearly 900 Cal. in an adult, but 

 not more. 



