224 MAKITAL OF CATTLE-FEEDING. 



bonic acid, water, and otlier products ; tliat tins process re- 

 sults in an increased excretion of carbonic acid and water, 

 wliile the excretion of nitrogen remains, in most cases at 

 least, unaltered ; and finally, that the amomit of work per- 

 formed is in many cases greater than can be accounted for 

 by the amount of protein which the urinary nitrogen shows 

 to have been decomposed. 



All these facts are well ascertained, and they enable us 

 to frame an hypothesis which, though confessedly but a 

 rough and approximate one, is still considered by many 

 high authorities to accord more closely with the facts of 

 the case and with our general conceptions of vital activity 

 than those which place the source of muscular power in 

 protein on the one hand, or non-nitrogenous matters on 

 the other. 



This hypothesis supposes that during rest some of the 

 substances of the muscle-cells decompose into simpler com- 

 pounds, and in so doing set free their latent energy, and 

 that this energy, instead of appearing as heat, etc., is used 

 to build up out of other constituents of the cell a still more 

 complex compound, containing more potential energy than 

 its components, just as one portion of society may acquire 

 wealth at the expense of another portion without increas- 

 ing the total wealth of the comnnmity. 



The substances which are thus -"synthesized" are pro- 

 tein, non-nitrogenous matter from the blood, and oxygen. 

 Tlie hypothetical compound thus formed, after accumulat- 

 ing to a certain extent, decomposes during rest as rapidly 

 as it is formed. When the muscle is called on to perform 

 work, however, it splits up rapidly, yielding carbonic acid, 

 water, and other non-nitrogenous matters, and a nitro- 

 genous compound, and giving forth the amount of force 

 which was required to form it. The non-nitrogenous sub- 



