164 THE HUMAN MOTOR 



and animals, the admission of the gas utilised in combustion is 

 perfectly regulated and exactly adapted to the necessities of the 

 expenditure, regardless of the quality of the food. The air cir- 

 culates in a respiratory chimney/' whose shape provides 

 numerous surfaces of contact between the oxygen and the blocd. 

 The work of the respiratory muscles increases with increased 

 expenditure (dynamic state) and influences the value of that 

 expenditure ; the regulation of the living machine is assured by 

 the respiratory nervous centres ; without prejudice to the general 

 control of the brain. 



110. Recapitulation. The combustible of the human motor 

 must contain a proportion of 1 gramme of proteids per kilo- 

 gramme of the weight of the body, and enough carbo-hydrates 

 to suffice for the muscular woik (external and internal) ; but, 

 for the regulation of the temperature, the fight against cold, the 

 nature of the combustible is indifferent. However, it will be 

 noticed that fats, at equal weights, are the most exothermic, 

 being 9-40 Cal. per gramme of reserve against 4-15 Cal. and 4-40 

 Cal. ( 96). They are therefore economical, and experiment has, 

 moreover, shown that the organism chooses them for its " thermo- 

 genesis " ( 170). The above table shows the variations of the 

 respiratory quotient, and the consumption of oxygen as functions 

 of work and alimentation. (*) The expenditure is calculated from 

 the volume of the gas consumed at 4-90 Cal. per litre measured at 

 C. and 760 millimetres barometric pressure, the alimentation 

 being mixed. If the alimentation is pure the table in para. 101 

 can be used, and in the case of fasting an average value of 4-60 

 Cal. per litre of oxygen can be taken. 



(!) Atwater and Benedict (Bulletin, No. 136, p. 167, Table 97, 1903). 



