no POULTRT-CRAFT. 



(2). Carbohydrates (technically, "nitrogen-free extract"), carbonaceous 

 matter, principally starches. Carbohydrates form the bulk of the dry matter 

 in nearly all foods, and are the principal sources of heat and energy, which, 

 as is well known, are convertible. 



(3). Fats. Found to some extent in every article of food. Their function 

 is to furnish heat and energy, on demand, in addition to the supply from the 

 carbohydrates, to store up fat as a reserve of heat and energy within the 

 body, and to furnish the material for elementary growth cells which are 

 developed by the protein. Fat also enters largely into the composition of the 

 egg, forming nearly one-half its solids. 



As far as known these elements have the same properties, no matter what 

 the form in which they occur. In the last effect, it makes no difference 

 whether the sources of the protein, carbohydrates and fats assimilated were 

 vegetable or animal. It is known, however, that in animal foods the elements 

 are more completely digestible than in grains, and more digestible in grains 

 than in vegetables and fruits ; and it has been observed that of two foods, one 

 animal, the other vegetable, containing large and nearly equal proportions of 

 protein or of fat, the animal food is generally preferred is more palatable. 

 In formulating working standards and in making practical applications of the 

 laws of foods, using the chemical analyses of articles, the principal elements 

 are regarded as completely digestible. The subordinate elements are regarded 

 as indigestible, and are omitted from calculations. The results thus obtained, 

 while not strictly accurate, are sufficiently so for practical purposes. 



SUBORDINATE FOOD ELEMENTS are : 



(i). Ash lime and other mineral matter, occurring generally in very 

 small quantities, except in such articles as bone and shell partly digestible. 



(2). Fiber, husks or waste matter mostly, if not completely indigestible. 



151. Principal Elements Can Mutually Assist Each Other. The 



principal food elements, though having each its special function, are not wholly 

 independent. Within limits they may be said to be able, on occasion, to do 

 each other's work. The relations of fats and carbohydrates have been indi- 

 cated. Carbohydrates are cheap fuels for ordinary use. Fats are expensive 

 fuels for emergency use. Any deficiency of carbohydrates and fats in a ration 

 will be at least partially made up by the diversion of a part of the protein from 

 its proper function. With a sufficiency of carbonaceous matter, the entire 

 consumption of protein is available for growth and maintenance. Further than 

 this, a deficiency of protein is not made up from the other elements. Scientific 

 opinion as to the effects of feeding the various elements to excess is not unani- 

 mous, nor are any of its expressions decided enough to be taken as authoritative , 



