384 THE POPULAR SCIENCE MONTHLY. 



0'70. Other natural fat3 would give results differing little from 

 this ratio. 



The carbohydrates, on the other hand, contain relatively more oxy- 

 gen than the other classes of foods, and contain hydrogen and oxygen 

 in just such proportions as exist in water. Hence by their oxidation 

 just enough oxygen must be consumed to convert the carbon to car- 

 bonic-acid gas, e. g. : 



C fl H 10 O 6 + 120 = 6CO a + 5H 3 0. 



Glycogen. 



C 6 H 12 6 + 120 = 6C a + 5H.0. 



Grape-sugar. 



The ratio is hence 1 for all this class, since the carbonic acid formed 

 is equal to the volume of the additional oxygen consumed. It follows, 

 then, that the oxidation in the organism of carbohydrates would tend 



CO 



to cause the ratio - to approach unity. The extensive investiga- 



Os 



tions of Regnault and Reiset on small animals have shown that with 

 carbohydrate food the ratio does approach unity, sometimes almost 

 attaining it, though of course it is impossible to eliminate entirely the 

 decomposition of fats and albuminoids in the organism, and hence the 

 ratio is kept below that figure. 



So, also, as we have seen above, the tendency of muscular exertion 

 is to increase this ratio and cause it to approach unity. The evidence, 

 then, seems to point with tolerable conclusiveness to the fact that the 

 immediate fuel-material is mainly non-nitrogenous and carbohydrate 

 in its character.* To what extent this supply of carbohydrates is de- 

 rived from the glycogen of the muscles, to what extent from sugars 

 absorbed from digestion, or produced from the glycogen of the liver, 

 is not yet established with sufficient accuracy, though the participa- 

 tion of the muscle-glycogen is hard to doubt. 



We have said the immediate fuel-material is apparently carbohy- 

 drates, for the possibility still remains that this carbohydrate material 

 may itself be in part derived from albuminoids. It is certain that the 

 liver-glycogen is in great part, possibly entirely, derived from albu- 

 minoids. Parke's experiments, above mentioned, showing a continu- 

 ous elimination of increased quantities of nitrogen in the form of urea 



* It will, T think, be evident that the widely entertained theory of Herrmann, regard- 

 ing the chemical processes taking place during muscular action, is not contradicted by the 

 considerations here advanced. According to this theory, a complex nitrogenous substance 

 of the muscular tissue is decomposed during muscular activity with evolution of carbonic 

 acid, and other non-nitrogenous residues, together with a simpler nitrogenous substance 

 which is supposed again to unite with other (non-nitrogenous) matter to form the origi- 

 nal compound, which may be again decomposed during contraction. This still leaves the 

 non-nitrogenous matter the fuel-material, but assumes it to be stored up in the form of a 

 combination with a complex nitrogenous substance which then yields it again in the form 

 of carbonic acid and water. This theory lies too far in the field of speculation for its 

 discussion to come within the scope of the present article. 



