Constituents of Animal Bodies 117 



by John L. Stone,* investigator and instruc- 

 tor in the College of Agriculture of Cornell 

 University, are appended : 



Principles of Feeding. — The various substances 

 found in animal bodies may, for convenience, be 

 grouped under four heads : (1) water; (2) ash, or 

 mineral matter; (3) fat; (4) nitrogenous matter 

 or protein. These substances occur in the animal 

 body in somewhat varying proportions, depending 

 upon age, condition, treatment, and other factors. 



Water is an essential constituent of the animal 

 body, and constitutes from 40 to 60 per cent of 

 its live weight. Ash occurs mainly in the bones 

 and constitutes from 2 to 5 per cent of the live 

 weight. The fat occurs in greatly varying pro- 

 portions, but rarely is less than 6 or more than 

 30 per cent. All those substances containing 

 nitrogen are classed as protein. They constitute 

 an important group, of which washed lean meat 

 and the white of ^gg may be taken as tj^es. 

 Proteids contain about 16 per cent of the element 

 nitrogen, and are the only class into the compo- 

 sition of which this element enters. All the 

 working machinery of the body, such as flesh, 

 skin, bones, hair, internal organs, brain and 

 nerves, contain a large proportion of protein. 



Composition of Food Materials. — The same four 



•Bull. 154, Cornell Exp. Sta. 



