The Source of Muscular Energy. 69 



employment of its power in doing tlie same piece of work; with 

 the same individual the quality and intensity of the work produces 

 great differences, and further researches are required to reduce 

 the variations in question by regular use to an individual and 

 perhaps a typical average value." 



97. The sources of muscular energy. — Wolff further saysi^ 

 '' The essential sources of muscular power are seen in the decom- 

 position processes in the body, i. e., in the destruction which 

 portions of the body or the food resorbed from the digestive tract 

 undergo by the passage of the plasma through the tissues. To 

 this end, as we have already seen in the case of fat-production, 

 both nitrogenous and non-nitrogenous substances contribute. As 

 these materials are resolved by the influence of oxygen into 

 simple groups of atoms, the energy of cheniical force which 

 previously linked the atoms together in more complicated group- 

 ings is set at liberty, and can be employed as kinetic energy for 

 the external work of the body. In a condition of rest, this energy 

 serves for the internal work of the organs or is converted into 

 electric current, etc. The animal body often stores up a certain 

 amount of energy; as soon as this store has been rapidly exhausted 

 by work, a period of rest is necessary to enable fresh material to 

 flow through the tissue-cells and generate fresh energy for the 

 production of more active work. The force-production and aU 

 phenomena resulting from the combustion of organic matter in 

 the animal body must obey the law of the conservation of energy." 



98. Conclusion. — Taking the experiments here presented and 

 many others by the investigators for guidance, we may conclude 

 that in the exercise of force there is greatly increased expenditure 

 of the n on -nitrogenous constituents of the food (carbohydrates 

 and ether extract), and but little of the nitrogenous. (444) At 

 the same time the importance of nitrogenous food must not be 

 under- estimated, for, as Wolff tells us: ''No one expects much 

 work from men or animals fed on a diet poor in nitrogen, such as 

 potatoes and rice. Fatness of body is never considered a sign of 

 muscular strength." 



» Farm Foods, pp. 85, 86. 



