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and fat make the richest food. Carbohydrates though less con- 

 centrated, are also highly digestible. Fibres are more or less 

 digested by ruminant animals, but they are not a desirable 

 component of food substances. The ash constituents of plants 

 are not altogether useless though in estimating the feeding 

 value of a crop, these are neglected. The bones and the ash 

 constituents generally of the animal frame are derived from the 

 ash constituents of plants, and hence they have-a great value. 

 Before giving the chemical composition of the principal 

 crops it is best to give at the outset the composition of the 

 principal articles of human food, as a. guide for judging the 

 value of all food substances and fodders. 



Average composition of the commonest food substances. 



w Albumi- Carbohy- ^., ^ 



Water ' noids. drates Flbre " Fat _ Ash ' 



Flesh ... 685 20-4 Nil Nil 10 ri 



Fish ... 826 15-8 Nil Nil -4 1-2 



White bread ... 35-4 9-5 52-8 Nil 1-2 ri 



Flour ... 12-5 1 1-3 74-6 Nil i-i -5 



Average cereal 117 9*12 71-2 3 32 



Average pulse 10 24 52-5 7 3-5 3 



Potatoes ... 77-9 2-1 18 i T -9 



Turnips ... 917 ri 5-3 i - 2 7 



Cabbages ... 89-5 1-5 7 n -i -8 



251. Composition variable. The composition of grain 

 and seeds is tolerably constant, but that of straw, leaves, 

 roots and tubers, varies very considerably according to the 

 variety, soil, manure and season. The same variety of wheat, 

 rice, maize or any other grain or seed has about the same 

 composition, but different varieties often differ very much in 

 composition. The hill rices, for instance, contain much more 

 fat than the ordinary rices. With regard to fodders the 

 chemical composition differs very much according as the crops 

 are cut in a mature or immature condition, and also accord- 

 ing to the process of drying they afterwards undergo. Too 



