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A MANUAL OF PHYSIOLOGY 



taken up by the muscle, and stored in some compound or com- 

 pounds, probably essential constituents of the living muscular 

 substance, which are broken down during muscular contraction, 



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8 



g e 



and more slowly during rest, carbon dioxide in both cases being 

 one of the end products. It is possible that there is an ascending 

 series of bodies through which oxygen passes up, and a descend- 



