THE SOURCE OF MUSCULAR POWER. 823 



the body during rest, and its connection with the laying up of a re- 

 serve of force : the oxygen enters into the supposed complex com- 

 pound much as the nitric-acid radicle enters into nitro-glycerine or 

 gun-cotton it is held in a state of unstable equilibrium, ready to enter 

 into new and simpler relations with its neighboring atoms, and to set 

 free the force by which it was placed in its unstable position. The 

 hypothesis explains also that necessity for albuminoids in the food of 

 the laboring animal which practical experience has shown to exist, as 

 well as the fact that there is no greater excretion of nitrogen during 

 work than during rest ; the proteine serves as the basis for the alter- 

 nate synthesis and analysis which constitute what might be called the 

 atomic mechanism of muscular activity without itself being destroyed. 

 Furthermore, it shows why we need rest after work ; in the first place, 

 the circulation must have an opportunity to remove those waste prod- 

 ucts which accumulate in the working muscle faster than they can be 

 carried off, and in the second place a fresh supply of force must be 

 stored up in the way described before it is ready to be used at the 

 command of the will. 



Thus this theory explains all the facts now known, and, while it 

 is but an hypothesis, it is still based on the " scientific use of the 

 imagination," and indicates the direction in which we may confidently 

 look for an advance of positive knowledge. 



If it be true, much of the current discussion upon the source of 

 muscular power is but a " strife of tongues " ; both proteine and non- 

 nitrogenous substance are necessary, and an inquiry as to which is 

 the source of the power would resemble an inquiry as to whether the 

 explosive force of nitro-glycerine was derived from the glycerine or 

 the nitric acid used in its manufacture, and would be a question of 

 metaphysics rather than of natural science. 



It might be asked, since this is a question of transformation of 

 energy, why we do not apply the law of the conservation of energy, 

 and from the heat of combustion of the various elements of food cal- 

 culate their value as reservoirs of force by Joule's formula. This has 

 been frequently attempted, notably by Fick and Wislicenus in their 

 experiments already alluded to. These investigators showed that the 

 amount of force contained in the proteine which was destroyed in their 

 bodies during the ascent of the Faulhorn was insufficient, if wholly 

 converted into motion, to raise their bodies to the height of the moun- 

 tain. 



Various other attempts at the same sort of calculation have been 

 made, with more or less of care and insight : we may mention here 

 those of Dr. Pavy, which rest on several assumptions of questionable 

 accuracy ; and those of Professor Flint, made upon the same plan, with 

 the object of showing the worthlessness of Dr. Pavy's an object 

 which he has doubtless attained. 



It would carry us too far to discuss here the value of these results, 



