INTRODUCTION 3 



Of all the elements necessary in a complete diet, the 

 most important are carbon, hydrogen, oxygen, and 

 nitrogen, and of these oxygen is chiefly required in the 

 free or uncombined state in which it occurs in the air 

 and is taken in by the lungs. The other three are 

 supplied in food, chiefly in the form of proteins, fats, and 

 carbo-hydrates. On chemical analysis, foods are found 

 to consist of certain proximate principles — viz., water, 

 nitrogenous compounds, fats, carbo-hydrates, crude fibre, 

 and salts, thus : 



Of these, the first requires little mention here except 

 to say that, whilst watep adds to the weight of the food- 

 stuff, it adds nothing to its energy-producing value. 

 The salts — often called the mineral matter or ash — 

 supply essential constituents of the body tissues ; they 

 assist in the processes of digestion ; and some of them, 

 such as the phospha.tes and the lime salts, are especially 

 useful in young growing animals for the formation of 

 bone, but they do not give rise to the production of energy 

 in the body, and for this reason are not included in the 

 so-called '* nutrients " of a food. 



The "crude fibre" consisting of cellulose and its 

 various modifications, such as lignin, is not only largely 

 useless itself as a food for horses, but since it encloses 



