INTRODUCTION 3 



portionately less serum. Skim-milk is the milk de- 

 prived of the bulk of its cream, and if the separation 

 of cream has been performed in a centrifugal separator 

 it is practically free from fat and contains only the 

 aqueous serum. This is termed separated or machine- 

 skimmed milk. 



When cream (or milk) is suitably agitated for seme 

 time, the fat globules coalesce to small granules, and 

 these after working together into a nearly homogeneous 

 mass form butter. This is chiefly composed of fat, but 

 contains some water and other constituents of milk. 

 The residue is termed butter-milk, which does not differ 

 greatly from skim-milk in composition. 



By treating milk with rennet, curd is separated ; this 

 carries down the bulk of the fat, and after pressing, 

 salting, and ripening, partly by the action of miero- 

 orgamsms and partly by the action of the natural 

 ferments of milk, it is converted into cheese ; cheese 

 consists essentially of fat, para-casein, and prc ducts de- 

 rived from the latter together with seme water and salts. 



The following Table gives the average morning and 

 evening milk for each month, and represents the per- 

 centage composition during 1911 : 



TABLE I 



