150 STORING UP OF OXYGEN. 



oxidation, still direct oxidation is not the immediate means 

 whereby muscular force is evolved, any more than it is of the 

 performance of any truly vital function. " It is also certain 

 that the chemical metamorphoses which furnish the force to the 

 muscles are, in part, not performed at the moment of the mus- 

 cular contraction" (Ranke, op. bit., 632). This relates chiefly 

 to the supply of oxygen, which is not, as was formerly supposed, 

 derived directly from the oxygen of respiration at the time, but 

 from oxygen already stored up in the organism in some mode not 

 yet settled. The proof of this is that, according to the experi- 

 ments of Pettenkofer and Voit, the expired carbonic acid is no 

 measure for the quantity of oxygen inspired at the same time, 

 and the quantity of carbonic acid expired during the day 

 greatly exceeds the oxygen inspired during the same time, even 

 if the body be at rest, but still more (to the extent of double) if 

 working, while the contrary 'is the case during the night. Thus 

 in the waking day the expiration of carbonic acid is due in 

 great part to the 'surplus of oxygen inspired during the pre- 

 ceding night, and stored up in the system ; and in fact the 



pendent on oxidative processes alone, although this may be the most 

 frequent example of the general law that force is set free by every 

 chemical process through which stronger affinities than before ore 

 satisfied. An example of a non-oxidative process whereby, neverthe- 

 less, heat is evolved, is given by the alcoholic fermentation of sugar. 

 As shown in the diagram, the affinities of the C atoms, which in the 

 sugar-molecule were unsatisfied either by the carbon or the hydrogen 

 affinities, are after the splitting up satisfied by the O affinities ; but as 

 the attraction of O to C is greater than C to C or to H, an evolu- 

 tion of force must take place by this atomic change of position" 

 (Hermann, 191). 



Sugar = C 6 Hi, O 6 



Splits up into carbonic acid and alcohol 



C 2 H 6 C0 2 CO, C 2 H 6 



