ALIMENTATION AND THE EXPENDITURE 157 



of proteids. Even when fasting it obtains them from its own 

 substance. Also the quantity of proteids utilised is never enough 

 to cover the expenditure incurred when working. A demonstra- 

 tion of this was given by Fick and Vislicenus in their ascent of 

 the Faulhorn f 1 ) ; the urea of the urines collected, gave by calcu- 

 lation ( 101) a value for the expenditure which was much lower 

 than that of the work done. Therefore the organism does not 

 accept a combustible exclusively proteid. Chauveau, and, later, 

 Atwater ( 99) confirmed this result ; it is thus that in an expendi- 

 ture of 9,314 calories, only 478 calories had a proteid origin ( 2 ) ; 

 it rarely reaches 500 or 600 calories. Hence living motors consume 

 ternary aliments abundantly that is, fats and carbo-hydrates. 

 Can we say that these behave in the same way as the proteids and 

 are expended accoiding to theL calorific p"owers ? To take a 

 numerical example, 1 gramme of reserve fat has a calorific equi- 

 valent of 9-4 Calories, while 1 gramme of carbo-hydrates is equiva- 

 lent to 4-2 Calories. Can vve.. therefore, replace 1 gramme of the 



9-4 



former by - = 2-249 grammes of the latter ? 



Q'A 



To admit this is to accept the " isodynamic theory," by virtue 

 of which the immediate principles can be substituted for each 

 other, in proportion to their heats of combustion, 4-20, 9-40 and 

 4-75 respectively, according to Berthelot's determinations with a 

 calorimeter. This would lead to the following proportions by 

 weight: Carbo-hydrates 100, Fats 44-7, Proteids 88-4. 



Experiment has not always confirmed this doctrine, for 

 Atwater J s method gave 4-40 cal. instead of 4-75 cal. for the heat 

 of combustion of the proteids ( 96). It also showed that, for the 

 same amount of work done, under approximately identical con- 

 ditions, the expenditure is less with carbo-hydrates than with 

 fats ; or a sugar ration is more economical than a fat ration ; 

 which presumes a lower value for fats -than that assigned to them 

 theoretically. In one case, it was even found that the calculation 

 of the expenditure based on an isodynamic utilisation of 7,744 

 calories of fat, was 667 calories in excess of the measured 

 expenditure^ 3 ) The isodynamic theory may be correct for a 

 man in repose, nourished by a mixed ration abundant in carbo- 

 hydrates, but is not justified if the man does a great amount 

 of work or takes insufficient nourishment. In these conditions, 

 Chauveau and Seegan considered that the reserves are transformed 

 into glucose in the living cells, and are consumed in this state. 

 Two quantities of aliments are thus energetically equivalent if 



(*) Fick and Vislicenus (Arch. Sc. Nat., 1868, p. 273). 



( 2 ) Atwater and Benedict (Bulletin, No. 136, p. 188, 1903). 



( 3 ) Atwater and Benedict (Bulletin, No. 136, pp. 175 and 307, 1903). 



