ALIMENTATION AND THE EXPENDITURE 147 



Carbo- 

 hydrates Fats Proteids 

 Calorific power of a litre of 

 oxygen at and 760 milli- 

 metres 5-05 Cal. 4-70 Cal. 4-53 Cal. 



Respiratory quotient CO 2 /O 2 ... 1-00 0-71 0-82 



In reality, it is not known in which molecular state the albumen 

 is oxydised or at what stage precisely the combustion stops. 

 Numerous experiments show that hydro-carbonised alimentation 

 raises the respiratory quotient almost to unity ; that fatty 

 alimentation lowers it on an average to 0-73, and that the value 

 is from 0-82 to 0-83 in a proteid alimentation. ( l ) This latter, for 

 the same expenditure of energy, causes a higher consumption 

 of oxygen, ( 2 ) because proteids are the least " thermogenetic." 



Experiment has demonstrated the truth of this and has shown 

 that the absorption of oxygen used in combustion is least in the 

 carbo-hydrates, somewhat more in the fats, and most in the pro- 

 teids. All this shows the value of the oxygen method. ( 3 ) 



102. Limitations of the Energetic Value of Aliments : Nervine 

 Aliments. Whilst explaining that the alimentary substances 

 turn into true combustibles, it has been stated that the organism 

 is never indifferent to their character ( 94) ; for it must be able 

 to assimilate them, and draw reserves from them. Heat engines 

 whether they have an internal or external furnace on the 

 contrary, burn any combustible capable of developing heat. But 

 there are substances whose action appears to act on living matter 

 directly, that is, on the muscular or nervous fibre, and which are 

 accompanied by effects depending very little on their calorific 

 energy. They have been called " nervine aliments " ; and 

 because certain of them reduce the energetic expenditure, they 

 are also called " aliments of economy " or " dynamophores." 

 They are notably the following : coffee, tea, mate, cocoa, kola, 

 pimento, butyric acid, sodium chloride, ordinary alcohol, etc. 



As a matter of fact, their action is singularly obscure : the 

 majority of them, in strong doses, are toxic, as is shewn by the 

 nervous troubles they cause. 



Some of them play a part in the alimentary metabolism, 

 perhaps as cellular excitants, analagous to the action of zinc salts 

 on the " Aspergillus " ( 94) ; and their toxic character is 

 weakened in a number of people who absorb certain of these 

 substances frequently. 



( l ) See particularly ( 103) the experiments of Atwater on man (Bulletin, 

 No. 136, p. 167, 1903). 



( a ) A. Chauveau (Comptes Rendus Sciences, 28th Jan., 1907, p. 173) ; 

 Jules Amar (Ibid., Feb. 19th, 1912, p. 528 ; Journal de Physiol., 1912, p. 298). 



() A. Chauveau (Comptes Rendus Sciences, vol. cxxxii., p. 194, 1901 ; 

 Oct., 1904, p. 53). 



