MUSCLE AND EXTRACTIVES. 341 



Q ; H 12 O 6 + H 2 O and was long spoken of as muscle sugar. 

 It is not a true carbohydrate, however, but an aromatic prod- 

 uct C H (OH) 6 , that is, hexahydroxybenzene. The amount 

 found in muscle is very small and how it is derived is not 

 known ; but it is not peculiar to these tissues, as it occurs in 

 other organs of the body and also in many vegetable sub- 

 stances. It may be extracted from muscles without much 

 trouble and when pure is found to be a w^hite crystalline pow- 

 der melting at about 220. It is very soluble in water to 

 which a sweetish taste is given, and in presence of alkali is 

 not a reducing agent for metallic solutions. Although the 

 usual structural formula does not show an asymmetric car- 

 bon atom the substance is optically active and exhibits a strong 

 rotation, both right and left forms being known. 



GLUCOSE. From what was said above about the transfor- 

 mation of glycogen it is not surprising that a small amount of 

 sugar should be found in the muscles; both maltose and glu- 

 cose have been detected. 



LACTIC ACID. Several forms of this acid are known, but 

 that occurring in the muscle is the dextrorotatory paralactic 

 or sarcolactic acid, C 3 H 6 O 3 . It is one of the a-hydroxypro- 

 pionic acids. There has been much speculation as to the 

 source of this acid in the body, but it seems most rational to 

 regard it as derived from the glycogen or sugar by a com- 

 paratively simple cleavage. It is also possible that in the 

 katabolic reactions of proteins lactic acid may result from a 

 splitting of the carbohydrate group. The acid is not very 

 readily detected in the living muscle because it is probably 

 oxidized or removed too rapidly by the fluid circulation. In 

 the dead muscle, however, it may accumulate to the extent of 

 half a per cent or more. The living muscle shows a neutral 

 or slightly alkaline reaction, while in the dead muscle the 

 increase of lactic acid changes the reaction. 



The lactic acid of the muscle probably results from an en- 

 zymic cleavage. In the aseptic autolysis of liver paralactic 

 acid has been recognized among the products, and this fact 



