CHAP. IT.] OF ALIMENTS. 467 



sea salt). Likewise urea, which contains still a great deal of 

 azote, has no alimentary value. 



Experiments have demonstrated that the animal machine needs 

 alike ternary aliments and quaternary aliments. Diet exclu- 

 sively non-azotised and diet exclusively azotised equally produce 

 the same disorders as abstinence. The equilibrium between the 

 azote absorbed and the azote expended is maintained on the sole 

 condition that the same equilibrium is also maintained as regards 

 carbon (Yoit, Boussingault). 1 



Man requires therefore a mixed diet, compensating at the 

 same time the losses of movement and the losses of substance. 

 The greater the expenditure of muscular force and the lower the 

 temperature, the larger must the proportion of ternary substances 

 be which enter into the alimentation. The inhabitants of hot 

 countries have need of few aliments. On the contrary, the Es- 

 quimaux of the Arctic regions eat every day 8 kilogrammes of 

 raw flesh, containing about a third of fat ; they drink seal-oil, 

 and swallow pieces of congealed whale-oil. Dr. Hayes states that 

 his European mariners, passing the winter in the polar regions, 

 had to restrict themselves to the diet of the Esquimaux. 



But the dynamical value of quaternary substances is never- 

 theless very considerable. In his Traite de Zootechnie, 2 M. A. 

 Sanson has tried to determine the dynamical coefficient of these 

 substances. For that purpose he compared the sum of kilo- 

 grammetres furnished in a day by the omnibus horses and the 

 post horses of Paris with the weight of albuminoidal substances 

 contained in their alimentary ration. Deduction made of the 

 portion of albuminoids necessary to the simple maintenance of 

 the animal, conformably to empirical data, he thought that he 

 had nothing more to do than to divide the sum of the kilogram - 

 metres by the number of grammes of albuminoids consumed by 

 labour. By proceeding thus it is found that in the horse 1 

 kilogramme of albuminoidal substances produces in round 



1 Annales de Chimie et de Physique, 3* serie, 1846, t. XVI U. 



2 A Sanson, Traite de Zootechnie, &c., 2 e edit., 1874, t. I. 



H H 2 



