126 THE CHEMISTRY OP THE FAEM 



consumed appears finally as heat : the remainder of the 

 food substance appears as animal increase. Of the 

 digested fat, 56*3 per cent, was stored up, and 43*7 per 

 cent, burnt in passing through the animal system. 

 Of the digested albuminoid, 44*7 per cent, was stored 

 up as nitrogenous tissue and fat, and 65*3 per cent, 

 burnt in the process. Of starch, 68'9 per cent, of its heat 

 value was stored up, while 41'1 per cent, disappeared as 

 heat. In the case of fibrous foods the losses rapidly 

 increase with the proportion of fibre present, the loss 

 in the case of meadow hay being 58'5 per cent., with 

 oat straw 62*4 per cent., and with wheat straw 82*2 per 

 cent. By a happy experiment Kellner showed that the' 

 very low results yielded by straw were not due to its 

 chemical nature, but to its mechanical condition. He 

 used in some of his experiments the straw pulp pre- 

 pared by paper manufacturers by boiling rye straw 

 under high pressure with an alkaline solution ; of this 

 softened, disintegrated cellulose, 88 per cent, was 

 digested by the oxen, and the digested matter yielded as 

 large a return in increase as was obtained from starch 

 or sugar. 



The very inferior results obtained from straw con- 

 firm the conclusions of Zuntz when using straw as 

 food for horses. The digested matter of the straw, 

 or its equivalent in other digested food, is so largely 

 consumed in providing the energy demanded by the 

 laborious process of straw digestion, that in the case 

 of the horse there was no balance remaining for other 

 animal requirements, while in the case of the ox only 

 17*8 per cent, of the heat value of the digested straw 

 was finally available for the production of animal 

 increase. 



