BIOLOGY. 245 



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fore be regarded as closely resembling those of fermentation and 

 putrefaction, and as depending not upon any muscular or nervous 

 hypothesis, but solely upon an incipient chemical decomposition 

 in combination with chemical electrometers. The Engineer. 



FOOD AS THE SOURCE OF MUSCULAR POWER. 



Liebig assumed that oxidation is the immediate result of the 

 disintegration of muscular tissue. He maintained that a portion 

 of oxygen separated from its combination in the blood, and trav- 

 ersed the walls of the capillaries with the nutritive fluid, and 

 that as fast as the new cells were built up by the one, the old ones 

 were oxidized b.y the other; the oxidized and lifeless products 

 being carried back to the blood, to be ultimately excreted from the 

 body as useless. The force liberated in this oxidation was the 

 force which contracted the muscle, and so did the work. He also 

 assumed that inasmuch as the muscular tissue was formed from 

 the flesh-formers of the food, and was almost identical in compo- 

 sition with them, the whole work of the body was derived from 

 the flesh-formers, which were therefore a true measure of the 

 amount of work which the body could accomplish, the amount 

 of urea excreted being taken as a measure of the amount of work 

 effected by the organism. 



Other physiologists have shown that the amount of work done 

 could not be measured by the urea excreted ; and Traube went so 

 far as to maintain that the oxidation of muscle, far from being the 

 sole cause of muscular work, contributed nothing whatever to it, 

 but that the whole work was done by the combustion of fats and 

 hydrates of carbon, as sugar, starch, etc. [For the experiments 

 of Fick and Wislicenus, Frankland, etc., see "Annual of Scien- 

 tific Discovery " for 1866-67, pp. 286-292 ; it is there shown that 

 the oxidation of muscle will not account for one-half of the actual 

 work done.] 



Between these opposite views of the origin of muscular power 

 is a third, by Mayer, founded upon consideration of the function 

 which the blood fulfils in the matter. Muscular contraction is 

 attended with a more rapid consumption of the oxygen of the cor- 

 puscles. Mayer makes the blood the seat of all oxidation, and 

 therefore the originator of all force in the body. Some part of 

 this force is evolved in the form of muscular work, the greater 

 part of the remainder in that of heat. How it comes about that 

 oxidation inside a capillary is converted into muscular movement 

 outside, is not ascertained, though the conversion is probably 

 effected under the control of the nervous system, some of the force 

 set free taking the form of electric currents. If Mayer's hypothe- 

 ses be true, the controversy between the followers of Liebig and 

 of Traube would be meaningless ; for as both fats and carbohy- 

 drates on the one side, and the products of muscle metamor- 

 phosis on the other, are oxidized in the blood, both may equally 

 be supposed to be originators of muscular power. The establish- 

 ment of this hypothesis would not help us much in the solution of 

 the question, What kind of food is most suitable for the man 



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