464 GRASSES OP IOWA. 



CHEMISTRY OF FOODS AND FEEDING. 



The value of any substance for use as a food depends 

 largely upon two important factors ; first, that of chemical 

 •composition, and second, the digestibility of the constituents 

 which form the substance. 



In connection with the study, the idea of food implies the 

 fact that the material has in it certain constituents which the 

 animal can use and under certain conditions they will become 

 available to supply the demands of the various parts of the 

 body so that a condition favorable for existence and growth is 

 maintained. 



These demands, which nature makes upon an animal in 

 order that it may live, are largely in the form of heat to keep 

 the body at a certain temperature, material to supply the mus- 

 cular force in order that they may exert themselves when 

 necessary and for the growth of the body. 



The constituents which are found in the various foods may 

 be classed as follows: 



( Water. 

 Inorganic -| Salts, such as common salt, phosphate of lime, carbonate 

 ( of potassium, and other salts. 



Organic ^ Nitrogenous, such as curd in cheese, albumin in egg, etc. 

 I Non-nitrogenous, such as starch, sugar, fats, etc. 



As an illustration, if we should make an analysis of a sub- 

 stance such as gluten meal, the results would be stated after 

 the following outline: 



Water 9.93 1 



Fat 13.46 I 



Protein 33.34 [ Containing albuminoids 33. 10. 



Crude Fiber 33.10 1 



Ash 1.04.1 



The amount of water present in a substance varies largely 

 according to the nature of the substance, whether green or 

 dry. The term fat is that part of the substance which is 

 extracted with ether. This extract is also known as crude fat 

 from the fact that the ether extracts the waxes, coloring mat- 

 ters, besides the fat that is present in the .food. The term 



