GBOWTR OF ANIMALS ; ANIMAL FOOD. 143 



Mineral Salts. — These are contained in ordinary fod- 

 ders in sufiB-cient quantities to supply the needs of the 

 animal body. 



The Chemical Analyses of Animal Poods. — By 

 means of chemical analyses the amount of moisture and 

 of the various groups of food compounds described as 

 contained in a food, are determined ; viz., albuminoids, 

 fats, carbohydrates, and mineral matter. This grouping 

 is, however, quite incomplete, though serving an excel- 

 lent purpose in indicating feeding value, and as a means 

 by which a comparison may be made of the various food 

 products. 



Water or Moisture. — Water or moisture is deter- 

 mined by drying at a temperature of boiling water. 



Crude Protein. — The nitrogenous substances are found 

 by determining the nitrogen, and multiplying the percen- 

 tage found by the factor 6.25, on the assumption that 

 all of the nitrogen is in the form of albuminoids, which 

 contain on the average sixteen per cent of nitrogen. The 

 substance found in this manner is called "crude protein." 

 In many cases, however, the nitrogenous substances, not 

 in the form of albuminoids, as amides and amines, and 

 contained in considerable amounts in immature plants, 

 are determined separately and deducted from the total 

 crude protein found, in which cases the results are stated 

 as " true albuminoids '' and as " non-albuminoids." 



Fat. — The content of fat is determined by extract- 

 ing with ether, or other solvents, and the result is stated 

 as crude fat or extractive matter, since other substances, 

 as gums and coloring matter, are extracted to some ex- 

 tent along with the fat. These may, however, be sep- 



