DEFINITION 3 



Marked improvements have been made in the manufacture 

 of butter b\- the adoption of scientific methods and the use of 

 modern equipments. Changes have been made in the period of 

 lactation. Formerly the cow furnished miilc only for her young. 

 Through the efforts of man, by breeding and selecting, the period 

 of lactation has been lengthened until at the present time it 

 extends over a period of ten months. The cow at the present 

 time is recognized as one of the most economical producers of 

 human food, hence, dairying has advanced rapidly in all coun- 

 tries that are adapted for the production of forage plants that are 

 suitable for feeding the cow. 



The United States at the present time produces five times as 

 much butter as any other country. The late census estimates 

 863,577,000 pounds of factory butter manufactured in 1920 and 

 675,000,000 pounds of farm butter. 



Notwithstanding the number of years that butter, milk and 

 other dairy products have been used for food, it is less than ten 

 years since the physiologists discovered that butter and milk 

 contained certain food elements that are essential for the growth 

 of the young that had escaped investigations made by eminent 

 chemists. This discovery was brought about by feeding experi- 

 ments by such noted physiologists as Dr, F. G. Hopkins of Cam- 

 bridge University, England, and Dr. E. V. McCollum of Johns 

 Hopkins University in this country. The discoveries made by 

 these eminent authorities will no doubt be the means of creating a 

 greater demand for dairy products of all kinds. 



Definition. — Normal milk is a hquid secreted in special glands 

 of all females belonging to the mammalian group. It is composed 

 chiefly of water, proteids, fats, sugar, and minerals. Coloring- 

 matters and gases and some organic acids are found in small 

 quantities. 



All normal milk from the different classes of animals, such as 

 mare, buffalo, goat, ewe, ass, and cow, has a general resemblance 

 in that it all contains water, fat, proteids, sugar, and ash. But 

 milk from different animals varies in the relative proportions of 

 its constituents. The chemical and ph},-sical properties are not 

 alike. When human milk is treated with half its volume of 



