334 



VETERINARY PHYSIOLOGY 



which carries with it a large amount of the fats. If cheese 

 is made before the removal of the cream it is rich in fats, if 

 after the removal of the cream it is poor in fats. Cheese 

 contains between 25 and 30 per cent, of protein, and between 

 10 and 30 per cent, of fat. It is as a source of protein that 

 it is of chief value. 



Percentage Composition of Milk. 



Cheese, when allowed to stand, affords a suitable nidus for 

 the growth of micro-organisms by the action of which the 

 proteins are digested into peptones and simpler 'bodies, and 

 the fats split up into glycerine and the lower fatty acids. 

 These free fatty acids give the peculiar flavour to ripe cheese. 

 The lactose is in part converted into lactic acid. 



2. Flesh. Under this head may be included not only the 

 muscles of various animals, but also such cellular organs as 

 the liver and kidneys. 



When free of fat, they contain about 20 per cent, of proteins. 

 These are chiefly native proteins, but a certain amount of 

 collagen is also present which yields gelatin on boiling. The 

 amount of fat may vary from almost nil in white fish to 

 about 80 per cent, in fat bacon. In animals specially fed, the 

 amount of fat may be enormously increased and even ordinary 

 butchers' meat may have more fat than protein. 



Flesh is thus a source of proteins and sclero-proteins, and 

 to a smaller extent of fats. The extractives include such 

 bodies as creatin, xanthin, inosit, etc. (see p. 40), which may 

 help to give the peculiar flavour to the flesh of various 

 animals. 



Flesh may be preserved in various ways e.g. by simply 

 drying, by salting, or by smoking. The result of each of these 



