106 PHYSIOLOGY FOR DENTAL STUDENTS. 



milk and the mixture kept warm, the clot which forms is called 

 casein. By separating the casein and allowing it to stand for 

 some time ferments, derived from moulds and bacteria, act on 

 it to produce cheese. The cheese, besides casein, contains much 

 fat and mineral matter. Cheddar cheese is especially rich in fat. 

 Cheese is a very concentrated article of diet and when taken in 

 moderation is thoroughly digested and assimilated. 



Cream consists of the milk fats with some of the constituents 

 of milk. It is the most easily assimilated of all the fats and is 

 hence very nutritious. When sweetened, flavored and frozen it 

 forms ice cream, which should not be regarded, as it usually is, 

 as a luxury, but as a highly nutritious food. It should not there- 

 fore surprise the indulgent parent when a child goes off its food 

 after visiting the corner pharmacy. On standing, cream ripens 

 (undergoes change due to bacterial growth) and if it be churned 

 the fat separates as butter. There is no foodstuff that contains 

 more calories and besides, the butter contains certain vitamines. 

 The fluid from which the butter separates, buttermilk, contains 

 practically no fat and is acid to the taste because of bacterial 

 action on the lactose producing lactic acid. Its influence on the 

 nature of bacterial growth in the intestines has already been 

 referred to. 



Eggs. The only point we need emphasize is the much 

 greater percentage of fat substances (lipoids) in the yolk than 

 in the white. One dozen eggs equals in food value two pounds 

 of meat. Eggs are therefore more costly than milk. 



Meats. The building stones of the protein molecule of meat, 

 for reasons which are obvious, are more nearly identical with 

 those of the tissues of man than are those of any other food. The 

 carbohydrate is however insufficient in amount, for which rea- 

 son we take potatoes with meat. The flavors of different meats 

 depend largely on the extractive substances which they contain. 

 These include creatin and purine substances. When a decoction 

 of meat is evaporated to small bulk, after precipitating all of the 

 protein, meat extract is prepared, which, like coffee or tea, has 

 no nutritive value but acts as a mild stimulant (caff em and theine 

 are chemically very closely related to the purine bodies of meat 



