1895.] PUBLIC DOCUMENT — No. 33. 17 



hand, contain but a small percentage. Cows, oxen, sheep 

 and horses have a digestive tract so arranged as to be able 

 to consume and digest large quantities of such coarse fod- 

 ders. 



J^unciions of the Cellulose. — It cannot form flesh, but 

 serves to produce vital energy and fat. 



(5) Crude Fat. 



By crude fat is meant not only the fats and oils found in 

 the various foods, but also the waxes, resins, etc. It has 

 also been termed " ether extract," because it is that portion 

 of the plant soluble in ether. Its elementary composition 

 is carbon, oxygen and hydrogen, with a much higher per- 

 centage of carbon than either the cellulose or extract matter. 



Functions of tlie Fat. — It serves the same purposes as 

 the cellulose ; it furnishes, however, two and one-half times 

 as much heat or energy as the cellulose. 



{4) Crude Protein. 



Protein is a general name for all the nitrogen-containing 

 bodies found in our common agricultural plants. It might 

 be called "vegetable meat." It corresponds, generally 

 speaking, to the lean meat of the animal body. All protein 

 or albuminoids contain on an average about 16.5 percent, of 

 nitrogen. It is, other things being equal, the most valuable 

 food constituent of the plant. Its elementary composition 

 is carbon, nitrogen, oxygen, hydrogen, phosphorus and 

 sulphur. 



Functions of the Protein. — The protein is a source of 

 energy, and is tJ(e only source of flesh. It also has been 

 considered a source of fat, although much doubt has lately 

 been thrown upon this idea. 



{5) Extract Matter. 



The so-called non-nitrogenous extract matter consists of 

 the starch, suijars and sums. A large part of the extract 

 matter of the coarse fodders (one-third to one-half) consists 

 of the M'ood gums or pentosans. It has been shown that in 

 the majority of cases the pentosans are as valuable for food 



