134 THE CHEMISTRY OP THE FARM 



The amount of total dry matter is seen to be toler- 

 ably uniform throughout the various classes of dry 

 foods, the foods richest in fat being generally the 

 driest. Corn and straw in bulk will frequently con- 

 tain a somewhat larger amount of water than that 

 mentioned in the table. In green fodder and roots 

 the proportion of water reaches its maximum. Of the 

 roots and tubers, potatoes contain the largest, and 

 white turnips the least proportion of dry matter. The 

 influence of the proportion of water on the nutritive 

 value of a food is discussed on p. 165. 



We have already seen (Chapter VII.) that fat and 

 albuminoids are the most concentrated forms of food 

 which an animal can consume ; those foods which are 

 rich in fat and albuminoids have, therefore, if digestible, 

 the highest nourishing value. At the head of all foods in 

 this respect stand the various descriptions of oilcake ; 

 they are, without doubt, among the most concentrated 

 foods at the farmer's disposal. Linseed cake, even 

 when pure, varies a great deal in composition, accord- 

 ing to the kind of linseed and the amount of pressure 

 used. Cakes made from East Indian seed will usually 

 contain 25 — 30 per cent, of nitrogenous substance ; 

 cakes from Eussian seed 27 — 33 per cent. ; cakes from 

 American Western seed 34 — 38 per cent. The oil in 

 American cakes is about 7 — 10 per cent. ; in ordinary 

 English and Russian pressed cakes 9 — 13 per cent. ; 

 in a few English and Russian cakes 15 — 16 per cent. 

 Decorticated cotton cake and earthnut cake are, when 

 of good quality, equal or superior to linseed cake, but 

 they are at present but little used by the English 

 farmer. The oil in decorticated cotton cake varies 

 from 9 — 17 per cent., according to the degree of 

 pressure used. Pure oilcakes contain no starch. 



