CHAPTER II. 



NUTRITION PROPER ANABOLISM FOOD PREPARATION 



DIGESTIVE SYSTEM. 



This includes all the changes from crude food to fin- 

 ished tissue. 



SECTION I. 



Food: its Kinds and Uses. 



Definition. — The word food is used in a wider and a 

 narrower sense. In the wider sense it includes all sub- 

 stances the ingestion of which is necessary to life. In 

 this sense it includes water and air and many salts. In 

 a narrower sense it means such substances as are used 

 for tissue building and for force making. It is in the nar- 

 row sense that we shall use it here. 



Kinds. — In this sense there are three kinds of food, 

 viz., albuminoids, amyloids, and fats. The first are com- 

 posed of C, H, O, N, and sometimes a little P and S, and 

 are therefore called quaternary compounds, or often ni- 

 trogenous compounds; the second, of C, H, and O, the 

 two latter in proportions forming water, and are there- 

 fore called carbohydrates j and the third, also of C, H, 

 and O, but the C in excess and the O in deficit. The 

 last two are called ternary compounds. Examples of 

 the first are found in albumen (white of egg), fibriti (lean 

 meat), gluten of wheat and other grains, legumin of 

 peas, beans, etc., and protoplasm, or living substance of 

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