92 THE CHEMISTRY OF THE FAR1T. 



carbo-hydrates also include various substances of little 

 feeding value. The same weight of dry matter in crude 

 foods of this class has thus a decidedly less nourishing 

 value than in foods consisting entirely of matured grain. 

 Foods belonging to different classes cannot safely be 

 compared on the basis of their composition. 



Most foods supply a sufficient quantity of: the ash 

 constituents which are required for the formation of bone 

 and muscle ; the chief of these are phosphoric acid, lime, 

 and potash. The oilcakes and bran are the foods richest 

 in phosphoric acid ; straw and meadow hay are the foods 

 poorest in this constituent. Lime is most abundant in 

 clover hay, bean straw, and turnips, and occurs in least 

 quantity in the cereal grains and in potatos. Potash is 

 abundant in roots, hay, bean straw, bran, and oilcake, 

 and is found in smallest quantity in the cereal grains. 

 The proportion of phosphoric acid and potash in various 

 foods is shown in the table on page 139. 



Of all the ash constituents lime and soda are pro- 

 bably the most generally deficient. Maize is of all 

 ordinary foods (rice excepted) the poorest in lime ; it 

 certainly contains too small an amount for a rapidly 

 growing animal. At Eothamsted a mixture of coal 

 ashes, common salt, and superphosphate was used with 

 advantage in the case of young pigs fed solely on maize. 

 It must be recollected, however, that animals will gener- 

 ally receive no inconsiderable amounts of lime in their 

 drinkirg water, 



Circumstances producing Variatiou'in Composition. 

 The composition of all vegetable foods is liable to varia- 

 tion, depending on the state of maturity of the plant, and 



