INCOME OF MATTER 91 



most suitable. All mammals begin their 

 existence on milk. The tissues of a chick 

 are built up out of materials contained 

 within an egg. If, however, we analyze 

 food stuffs, or diets that are known from 

 experience to suit all dietetic requirements, we 

 find they always contain representatives of 

 the five proximate constituents found in 

 the tissues of the body, and which we 

 have considered. Thus a suitable dietary for 

 almost any animal, and certainly for men, 

 always contains proteins, carbo-hydrates, fats, 

 saline matters and water. Other substances, 

 such as the condiments that are often added, 

 are merely adjuncts to the diet. Thus milk 

 contains more than one protein substance, 

 the chief one being caseinogen, which yields, 

 when acid or rennin is added to the milk, a 

 protein, casein, the chief constituent of curd ; 

 a carbo-hydrate as sugar of milk ; a fat, 

 or rather several fatty matters that all together 

 form butter ; various salts (chiefly chloride of 

 sodium and phosphate of lime) ; and water. 

 These proximate constituents are found in 

 varying amounts in different articles of food 



