400 VICTOR C. MYERS 



as a result of the post-mortem formation of lactic acid, increasing the 

 hydrophylic properties of the protein colloids of the muscle. 



The so-called extractives of muscle are of considerable interest and 

 importance. Including the inorganic salts they constitute about 2 per 

 cent, of the tissue, the organic material amounting* to 0.7 per cent and 

 the inorganic to 1.3 per cent. The organic material is ordinarily divided 

 into two groups, the non-nitrogenous and the nitrogenous. To the former 

 group belong glycogen, glucose, para- or sarcolactic acid and inositol, 

 and to the latter such substances as creatin, the purin bases, xanthin, hypo- 

 xanthin and guanin, carnosin, amino-acids and traces of creatinin, uric 

 acid and urea. 



Glycogen is a polysaccharide carbohydrate possessing some of the 

 properties of starch and dextrin. It is present in normal human muscle 

 tissue to the extent of about 0.5 per cent. From experiments on animals we 

 know that the amount may be markedly reduced by muscular activity. 

 Glycogen constitutes the muscles' reserve supply of energy. The glycogen 

 of the muscle together with that of the liver is apparently transformed to 

 glucose as needed. Judging from the observations of Palmer the glucose 

 content of the muscle is only about half that of the blood. Hopkins has 

 recently presented some interesting views regarding the transformation of 

 glycogen into mechanical and heat energy. The facts which he has brought 

 together indicate that there are two phases in muscular activity, the first 

 anaerobic and the latter aerobic. During the first, in which muscular con- 

 traction takes place, lactic acid is formed. During the second phase a part . 

 of the lactic acid is oxidized and transformed to carbon dioxid and water, 

 while a part is apparently reconverted to glycogen. The heat liberated 

 during this (second) period, however, is less than that required by the 

 oxidation of the lactic acid, and is apparently stored in the muscle in a 

 latent form for the next (first) phase of the reaction, when it is liberated. 

 The formation of lactic acid (producing changes in the hydrogen ion of 

 the muscle) apparently plays an important role in initiating the contrac- 

 tion of the muscle, while a combination of the glucose with phosphoric 

 acid i necessary to its cleavage into lactic acid. Rigor may take place in 

 the muscle as a result of severe exertion or from poor oxidation as in car- 

 bon monoxid poisoning, while rigor mortis may be prevented if a suffi- 

 ciently high concentration of oxygen is maintained to bring about an oxida- 

 tion of lactic acid. However, after a time irritability is lost apparently 

 as a result of the stabilization of the inorganic ions by the tissue. Although 

 inositol possesses the same empirical formula as glucose, it is a hexahy- 

 droxybenzene. However, it probably stands in fairly close relationship to 

 sugar since lactic acid may be formed from it, 



Of the nitrogenous extractives of muscle, creatin is present in much 

 the largest amount and is of the greatest interest, especially since it is 

 apparently the precursor of the creatinin of the urine. In 1913 Myers and 



