MUSCLE WORK. 567 



elusions from this experiment, but it seems to show that the proteins are not 

 consumed in work. 



The older investigations on the amount of fat in muscles removed 

 after activity and after rest have not led to any definite results. Accord- 

 ing to the investigations of ZUNTZ and BoGDANOW, 1 the fat belong- 

 ing to the muscle-fibres, which is difficultly extracted, takes part in 

 work. Besides these there are several researches by VOIT, PETTEN- 

 XOFER and VOIT, J. FRENTZEL, 2 and others which make an increased 

 destruction of fat during work probable or proven. 



If the results of the investigations thus far made of the chemical 

 processes going on in the active and inactive muscle were collected, 

 we would find the following characteristics for the active muscle: The 

 active muscle takes up more oxygen and gives off more carbon dioxide 

 than the inactive muscle ; still the elimination of carbon dioxide is increased 

 considerably more than the absorption of oxygen. The respiratory quotient, 



, is found to be regularly raised during work ; yet this rise, which will 



C0 2 



O 



be explained in detail in a following chapter on metabolism, can hardly 

 be conditioned on the kind of processes going on in the muscle during 

 activity with a sufficient supply of oxygen. In work a consumption 

 of carbohydrates, glycogen, and sugar takes place. The acid reaction 

 of the muscle becomes greater with work. In regard to the extent of 

 a re-formation of lactic acid opinion is divided. An increased consump- 

 tion of fat has occasionally been observed. The quantity of organic 

 phosphorus decreases, and an increase in the nitrogenous extractives 

 of the creatinine group seems also to occur. Protein metabolism has 

 been found increased in certain series of experiments and not in others; 

 but an increased elimination of nitrogen as a direct consequence of mus- 

 cular exertion has thus far not been positively proven. 



In close connection with the above-mentioned facts there is the 

 question as to the material basis of muscular activity so far as it has 

 its origin in chemical processes. In the past the generally accepted 

 opinion was that of LIEBIG, that the source of muscular action consisted 

 of a catabolism of the protein bodies; to-day another generally accepted 

 view prevails. FICK and WiSLiCENUS 3 climbed the Faulhorn and calcu- 

 lated the amount of mechanical force expended in the attempt. With 

 this they compared the mechanical equivalent transformed in the same 

 time from the proteins, calculated from the nitrogen eliminated in the 



1 Arch. f. (Anat. u.) Physiol., 1897. 



2 Pfliiger's Arch., 68. 



3 Vierteljahrsschr. d. Zurich, naturf. Gesellsch., 10, cited from Centralbl. f. d. 

 med. Wiss., 1866, 309. 



