122 THE PRINCIPLES OF AGRICULTURE. 



the amount of these substances that can be digested and 

 become useful to the animal. 



There are but few articles of food of which all the 

 albuminoids, fats, and carbo-hydrates can be thus di- 

 gested. The indigestible part is of no value for food. 



The table on the opposite page gives the percentage of 

 digestible albuminoids, fats, and carbo-hydrates contained 

 in the different articles of food, and the value of one 

 hundred pounds of each variety. 



In reckoning these values, the digestible albuminoids 

 and fats are, according to the usual custom, regarded as 

 worth 4j- cents per pound, and the digestible carbo- 

 hydrates as worth -f^ of a cent per pound. 



The results are, of course, only relative, and will vary 

 according to the market value of the standard articles 

 of food in any locality. If average hay is worth sixty- 

 four cents per hundred pounds, or 112.80 per ton, then 

 the other articles will be worth the sums given in the 

 table as compared with hay. 



If in any locality, or any year, the market value of hay, 

 corn, oats, or other articles commonly used, is greater or 

 less, upon the average, than the table indicates, then the 

 figures for all the articles mentioned must be increased 

 or diminished accordingly. 



The table affords a general guide for selecting and pur- 

 chasing foods, but it must not be depended upon for 

 great exactness. No article of food can, in reality, have 

 an absolute value of its own. The true value of any 

 article as food depends upon its combination with other 

 foods, the nature of the animal to which it is fed, and the 

 purpose to be accomplished. In order to make an intel- 

 ligent selection, it is necessary to understand what partic- 

 ular kinds of food are needed in the given case. 



