ALIMENTATION AND THE EXPENDITURE 163 



3. External Environment. With equal surfaces, radiation 

 increases with decrease in the temperature of the environment, 

 and, consequently the expenditure is proportionately increased 

 to compensate for this loss, this being a chemical law (Rubner). 

 In an environment the surrounding temperature of which is higher 

 than that of the body, bodies cannot reduce their expenditure, 

 because they are, in this case, under the law of the minimum 

 physiological expenditure ; they suffer, theref.ore, from the heat 

 that they produce and defend themselves from it by active pul- 

 monary and cutaneous vaporisation (see above, 104). This is 

 Rubner's f 1 ) " physical law.'* 



There is a sensibility in every one that reveals the action of the 

 " nervous centres/' 



EXPERIMENTS ON AN ADULT FOR 24 HOURS. 



109. Adaptation of the Respiratory Intensity to the Expenditure. 



The variations of the expenditure of the combustible cause equal 

 variations of the gas, utilised in conbustion, namely, the oxygen : 

 and the lungs are traversed by a current of air varying in 

 rapidity the number of respirations being modified (see 142). 

 Coal placed in a grate needs a sufficient draught in the chimney ; 

 but this draught, in industrial machines, cannot always be readily 

 adapted for every kind of combustible. On the contrary, in man 



(*) Rubner, Die Gesetze. (loc. cit., Ch. vdii.). Kraft, und Stoff. im Haus- 

 halte der Natur, p. 78. Leipzig, 1909 (very interesting little work). 



( 2 ) An average of 4-60 cal. is deduced from these figures. 



( 8 ) This is the value which corresponds to the normal ration in every day 

 life (see 105). 



