86 BRITISH DAIRYING. 



and liquid which, derived of course from the food a cow eats, 

 form for the necessary time a portion of the cow's body ; it is 

 not a mere direct change of that food into milk by the occult 

 agencies of the digestive organs. Be this as it may, however, 

 milk is an emulsion, and may be described as a highly-complex 

 fluid, most beautifully designed to nourish the offspring of the 

 animals which produce it. The specific gravity of milk, at a 

 temperature of 60 Fahr,, is about 1*030, varying a little from 

 this in some instances; while the specific gravity of water, 

 which is taken as a standard, is i-ooo. Milk is therefore 3 per 

 cent, heavier than water, while the cream of milk is about 

 i per cent, lighter than water. An average percentage of the 

 different elements of which milk is composed is as follows : 



Water . , . .87-25 per cent. 

 Butter . 3-50 



Casein .... 3-50 



Albumen . . 0-40 

 Milk-sugar . . . 4-60 

 Mineral substances . 0-75 



100-00 



111 extreme cases it has been found to exhibit the following 

 variations : 



Water . . 83-65 to 90-00 per cent. 

 Butter ,. ,-. s , i -80 to 5-30 

 Casein . a 3-00 to 5-00 

 Albumen . 0-30 to 0-55 

 Milk-sugar . 3-00 to 5-50 

 Mineral substances . 070 to 0-80 



These elements again are highly complex, but 1 will give 

 here only two, butter and casein, the most important by far. 

 Butter is made up of the following fats, in combination with 

 glycerine : - 



Myristine . 

 Palmitine . 

 Stearine . 

 Burine . . 



