MILK 



3802 



MILK 



ILK, a fluid secreted by the female of 

 all mammals for nourishing their young. The 

 milk of domesticated animals, including cows, 

 goats, sheep, asses and horses, has been used 

 from the earliest recorded time as food for 

 man. The milk of the cow, however, is the 

 only one now in general use in the United 

 States and Canada. 



Cow's milk is of chief commercial interest 

 and is also typical of all milks. It is an 

 opaque, whitish fluid, sometimes slightly yel- 

 lowish or bluish. Its specific gravity averages 

 about 1.032; that is, it is about three one- 

 hundredths heavier than water; a gallon of 

 milk weighs 8.6 pounds. It requires five and 

 one-half gallons of good milk to produce a 

 gallon of cream, three and one-half gallons to 

 make a pound of butter, and about one and 

 one-third gallons to make a pound of cheese. 

 Chemically considered, milk is an emulsion 

 (which see) of globules of fat in a water- 

 solution of casein, milk sugar, albumin and 

 ash. The water usually comprises 87.2 per cent 

 of milk; the fat is about 3.7 per cent; casein, 

 3 per cent; milk sugar, 4.9 per cent; ash and 

 albumin, each less than 1 per cent. The milk 

 from different animals varies considerably in its 

 composition, as does also the milk from the 

 same cow at different times. The percentages 

 given are merely approximate standards. 



When examined under a microscope the tiny 

 globules of fat can be seen. They vary greatly 

 in size, from one fifteen-hundredth to one 

 twenty-five-thousandth of an inch in diameter, 

 but it has been estimated that on an average 

 they are so small that one million of them are 

 contained in a pint. If milk is allowed to 

 stand in a cool place, these globules will gradu- 

 ally rise to the surface and form cream. It is 

 from the cream that butter, which is about 85 

 per cent fat, is made. Milk from which the 

 cream has been removed is called skim or 

 skimmed milk. 



The richness of milk that is, the percentage 

 of fat, casein, and other solids has been in- 



creased by careful breeding and care of cows 

 for centuries. The milk of wild cattle is not 

 nearly so rich as that of domestic varieties. 

 It is not true, on the other hand, that the pro- 

 portion of milk fat can be permanently in- 

 creased by feeding; so long as the food is 

 ample and wholesome it seems to have no 



Wisconsin 

 574-6 



Pennsylvania 

 354-3 



II linois 



Michigan 

 3035 



Minnesota 

 3519 



Ohio 

 3113 



Quebec 

 2701 



Figures Represent Millions of Pounds 



PRODUCTION IN A YEAR 



effect on the quality of the milk. It has been 

 noted, however, that there seems to be a direct 

 transmission of certain volatile-oil constituents 

 of feed to the milk, for example, when cows 

 eat garlic and onions ; and everybody is familiar 

 with the change in flavor which occurs when 

 the cows are first let out to green pasture in 

 the spring. 



