50 THE COMMON SENSE OF THE MILK QUESTION 



Perhaps it may be well to add to the foregoing 

 table a few w^ords of explanation. While the analysis 

 simply divides the constituents of milk into water 

 and solids, fat is really a semisolid. The solid con- 

 stituents proper are sugar, casein, albumin, and 

 mineral matter, called ash, or salts. Casein is a 

 protein compound of very great importance, forming 

 with albimiin the chief nitrogenous value in milk. 

 Curd is formed of casein through the action of acid. 

 It forms one of the principal ingredients of cheese — 

 about 25 per cent of its bulk — when coagulated 

 by the action of rennet. The ash or salts in milk 

 consists principally of phosphates and chlorides of 

 soda, potash, and lime.* 



DiAOBAM SHOWING COMPONENTS OF Cow'S MiLK 



With this explanation it will be easy to appreciate 

 the nutritive values of the various milks described. 

 It will be quite obvious, for instance, that the enor- 

 mous percentage of fat in the milk of the porpoise 

 — more than eighteen times that of woman's milk 



