n8 THE VITAL PROCESSES 



The Simple Foods, or Nutrients. From the great 

 variety of things that are eaten, it might appear that 

 many different kinds of substances are suitable for food. 

 When our various animal and vegetable foods are analyzed, 

 however, they are found to be similar in composition and 

 to contain only some five or six kinds of materials that 

 are essentially different. While certain foods may contain 

 only a single one of these, most of the foods are mixtures 

 of two or more. These few common materials which, in 

 different proportions, form the different things that are 

 eaten, are variously referred to as simple foods, food-stuffs, 

 and nutrients, the last name being the one generally pre- 

 ferred. The different classes of nutrients are as follows : 



Nutrients 



Proteids 



(Albuminoids) 



Carbohydrates 



Fats 



Mineral salts 



Water 



It is now necessary to become somewhat familiar with 

 the different nutrients and the purposes which they serve 

 in the body. 



Proteids. The proteids are obtained in part from the 

 animal and in part from the plant kingdom, there being 

 several varieties. A well-known variety, called albumin, 

 is found in the white of eggs and in the plasma of the 

 blood, while the muscles contain an abundance of another 

 variety, known as myosin. Cheese consists largely of a 

 kind of proteid, called casein, which is also present in milk, 

 but in a more diluted form. If a mouthful of wheat is 

 chewed for some time, most of it is dissolved and swal- 

 lowed, but there remains in the mouth a sticky, gum-like 

 substance. This is gluten, a form of proteid which occurs 



