40 VETERINARY PHYSIOLOGY 



In addition to the proteins, small quantities of other organic 

 substances are found in muscle. 



2. Carbohydrates. Glucose (C 6 H 12 6 ) is present in muscle, 

 as in all other tissues. 



Glyeogen a;(C 6 H 10 5 ) a substance closely allied to ordinary 

 starch, but giving a brown reaction with iodine is always 

 present in muscle at rest. If the muscle has been active, 

 the amount of glycogen diminishes, being probably converted 

 to glucose, and used for the nourishment of the tissue. (For 

 the chemistry of the carbohydrates, see p. 344.) 



3. Fat is present in small quantities in the fibres, and often 

 in very considerable quantities in the fibrous tissue between 

 the fibres. 



4. Inosite, formerly called muscle sugar, is present in small 

 amounts. It is not a sugar, but a benzene compound. 



5. Sareolaetie Acid. Hydroxy-propionic acid 



H OH 



I I II 

 H C C C H 



I I 

 H H 



This dextro-rotatory isomere of ordinary lactic acid is in- 

 creased in muscle during activity and during death stiffening. 



6. Extractives. If dried muscle is treated with alcohol a 

 series of bodies containing nitrogen may be extracted. The 

 chief of these is Creatin, or methyl-guanidin-acetic acid. 

 Guanidin C.NH(NH 2 ) 2 is a near ally of urea CO(NH 2 ) 2 , 

 being formed by replacing the with NH. 



Methyl-guanidin is produced by replacing an H in guanidin 

 by CH 3 - 



NH CH 3 



II I ' 

 H 2 N C N H 



If this is linked to acetic acid 



H NCH 3 H 



II I I II 

 H 2 N C N- -C C OH 



Methyl-guanidin H acetic acid 



is produced. 



