THE ACTIVE FORCES OF LIVING ORGANISMS 41 



way to this movement of deoxidation, since it is not 

 known whether the carbonic acid is produced at the 

 moment, or, having been previously formed, is merely 

 liberated. It is when we look at muscular contraction 

 from the point of view of the tissue which remains 

 after the oxygen has been expelled in the form of 

 carbonic acid or otherwise that it will appear to 

 us to be essentially a process of diminishing oxida- 

 tion. 



Although functional exercise is rightly regarded as Condi- 



tions most 



one of the conditions most essential to growth and favour- 

 development, there is probably no reason for sup- anaboiism. 

 posing that both katabolism and anaboiism take place 

 to ' an equal extent either during action or during 

 repose. The recuperative influence of sleep and the 

 lassitude and weakness which is caused by a lack of 

 it seem to point to the conclusion that the anabolic 

 factors predominate in this state. As to the general 

 character of sleep there can be very little doubt. 

 The decrease in the amount of carbonic acid produced 

 shows that it is essentially a period of diminished 

 oxidation, and this condition is, it would seem, the 

 most favourable for the building up, if not of all the 

 tissues in the body, yet at any rate of some of the 

 most essential, and especially, one may suppose, of 

 nervous matter, which in its chemical composition 

 contains relatively so small an amount of oxygen. 

 Absolute rest of body and mind has been recognised 

 to be one of the most efficient methods of restoring 

 nervous power. Amongst farmers it has long been 



