FAT MUSCLE. 265 



in small amount. Animal fats resemble in constitution the 

 vegetable oils already described." 



Fats from different animals, or even from different parts of 

 the same animal, have very different properties, especially as 

 to consistency and melting point. These depend upon the 

 relative amount of the glycerides of high melting point (e.g., 

 stearin, melting point about 63, and palmitin, melting point 

 62), and those of low melting point (olein, melting point 

 about -5). 



The average proportions of fat, water, and membrane (cell 

 walls, &c.) are given by Hammarsten as follows : 



Water. Membrane. F;it. 



Fatty tissue of oxen ... 9-96 1-16 88'88 



sheep ... 10-48 1-64 87-88 



pigs ... 6-44 1-35 92-21 



Fat may be produced in the animal from the fat contained 

 in the food or from proteids or carbohydrates. It forms a 

 valuable reserve from which the animal can draw in times of 

 scarcity of food, being the most concentrated form in which 

 energy can be stored in the animal. 



Muscle Muscular fibre consists of a sheath composed of 

 elastin and the contents, mainly albumins. 



Myosin is the principal albuminous constituent of the dead 

 muscle. Its amount varies from 3 to 11%. It is a globulin, 

 is soluble in neutral salt solutions, and coagulates at 56. 



Other albuminoids are found in muscle, of which musculin, 

 muscle-stroma, and myoglobin are the chief. 



There are also "nitrogenous extractives" present, the chief 

 being creatin (methyl-guanidine acetic acid), NH:C(NH 2 ). 

 N(CH 3 ).CH,.COOH + H 2 O; hypoxanthin or sarcin-, C 5 H 4 N 4 ; 

 xanthin, C 5 H 4 N 4 O 2 ; guanin, C. 3 H 5 N 6 O ; and carnin, C 7 H 8 N 4 O 3 

 + H 2 0. 



Muscle also contains inosit, C H 12 G +H 2 O (hexahydroxy 

 hexamethylene), glycogen, C G H 10 5 , a sugar (probably glucose 

 and most likely formed after death from glycogen), and sarco- 

 lactic acid, CH 8 .CH(OH).COOH. 



* v. p. 202. 



