252 POULTEY CTJLTTJEE 



(C), hydrogen (H), and oxygen (0), but the hydrogen is not 

 exactly twice the quantity the oxygen. Thus, the formula of 

 an animal fat, stearin, is C57H110O6, of palmatin CsiHggOe, 

 and of olein C67H104O6. 



The fats and oils constitute a second group of food nutrients 

 called hydrocarbons. 



A third food nutrient is the protein group. Nitrates are 

 taken up in solution by the roots of the plant which, upon 

 reaching the protoplasmic masses in the active plant cell, 

 nitric acid and sulphur, are united with starch or a starch deriva- 

 tive forming a protein compound. Protein is the nitrogen- 

 containing food nutrient, and contains carbon (C), hydrogen 

 (H), oxygen (0), nitrogen (N), and sulphur (S), the chemical 

 formula being as follows, C12H9O22N16S1. 



Vegetable albumins closely resemble the white of eggs. It 

 is coagulated by heat. The albuminoid in wheat is called 

 gluten. These three groups of food nutrients — namely, 

 carbohydrates, hydrocarbons, and protein — ^constitute the 

 organic portion of the food. 



Plants contain mineral matter which has been taken up in 

 solution during plant growth through the roots and deposited 

 in the plant tissues. Ash and water constitute the inorganic 

 nutrients of vegetable food. 



Organic matter is destroyed by fire. Inorganic matter 

 cannot be destroyed by fire, though its form may be changed. 

 Thus the water during burning of foodstuffs is changed in 

 form, but not destroyed. It enters the air as vapor, but be- 

 comes liquid again under favorable conditions, whereas the 

 protein burned is destroyed. 



The hydrocarbons or fats and oils are sometimes spoken of 

 as ether extract, because in analysis of foodstuffs they are 

 extracted by ether. Cellulose, an insoluble starch, the coarser 

 particles of feed, is spoken of as crude fiber. It is classed with 

 starch. 



The nitrogen-free extract belongs to the carbohydrate group. 



To summarize : The carbohydrate group includes the follow- 

 ing nutrients — ^starches, sugars, gums, and resins. The hydro- 

 carbon group — fats and oils. The protein group — ^the 

 nitrogen-containing food nutrients. 



