THE EARTH'S BOUNTY 



They are semi-solid, and form, with the serum, 

 a mixture called an emulsion. 



The solid constituents present in the serum 

 in largest quantities are sugar and casein. Al- 

 bumen and mineral matter are present in small 

 quantity, and there is also believed to be a 

 little fibrin, resembling the fibrin of blood. In 

 milk there is more sugar than any other solid 

 component. The milk sugar can be separated 

 from the solution, and brought into a solid 

 form; as sold, it resembles powdered white 

 sugar. It is used, to a considerable extent, by 

 druggists; also by manufacturers of certain 

 proprietary foods, especially those for infants. 



Sugar is the constituent of milk which un- 

 dergoes the greatest change when milk sours. 

 Casein and albumen of milk are the chief 

 nitrogenous constituents, and are generally 

 referred to as including all of this class of 

 substances in milk. They belong to the gen- 

 eral class of foods which includes the lean 

 meats and white of egg. Acid, or rennet, 

 causes casein to coagulate, forming curd, and, 



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