ALIMENTARY ENERGETICS. I4I 



and it is the need for the production of heat that 

 regulates the total demand for Calories which every 

 organism requires from its ration. It is not because 

 it produces too much heat that the organism gets rid 

 of it peripherally : it is rather because it inevitably 

 disperses it that it is adapted to produce it. 



Rubner's Experiments. — This conception of the role 

 of alimentation is based on two arguments. The first 

 is furnished by Rubner's last experiment (1893). A 

 dog in a calorimeter is kept alive for a rather long 

 period (two to twelve days) ; the quantity of heat 

 produced in this lapse of time is measured, and it is 

 compared with the heat afforded by the food. In all 

 cases the agreement is remarkable. But is it possible 

 that there should be no such agreement ? Clearly no, 

 because there is a well-known regulating mechanism 

 which always exactly proportions the losses and the 

 gains of heat to the necessity of maintaining the fixed 

 internal temperature. This first argument is, there- 

 fore, not conclusive. 



The second argument is drawn from what has been 

 called the iaw of surfaces, clearly perceived by Reg- 

 nault and Reiset in their celebrated memoir in 1849, 

 formulated by Rubner in 1884, and beautifully 

 demonstrated by Ch. Richet. In comparing the 

 maintenance rations for subjects of very different 

 weights, placed under very different conditions, it is 

 found that the food always introduces the same num- 

 ber of Calories for the same extent of skin — i.e., for 

 the same cooling surface. The numerical data 

 collected by E. Voit show that, under identical con- 

 ditions, warm-blooded animals daily expend the same 

 quantity of heat per unit of surface — namely, 1.036 

 Calories per square yard. The average ration intro- 



