68 THEORY OF FEEDING. 



RELIABILITY OF CHEMICAL ANALYSIS AS A GUIDE TO THE 

 FEEDING VALUE OF FOOD. 



We can draw only general conclusions from chemical 

 analyses of foods ; because (i) the respective feeding values of 

 the constituents of plants, as we have just seen, have not as 

 yet been accurately determined ; (2) the percentages of the 

 constituents vary greatly according to circumstances which 

 will be presently considered ; (3) neither the percentage nor 

 the presence of ferments is indicated by the analyses at our 

 disposal. 



FERMENTS IN GRAIN. 



We learn from the researches of Horace T. Brown (Chemical 

 Society's Transactions, 1890, pp. 458-528; and 1892, pp. 

 352-364) that certain grains contain a greater or less amount 

 of an unorganised ferment (enzyme) which, during digestion, 

 has the power to dissolve the walls of the cells of the grain, 

 and thus to expose their contents to the action of the digestive 

 fluids. The membrane which forms the walls of these cells is 

 thin, tender, and is composed of nearly pure cellulose. The 

 enzyme in question has no power to attack starch or the woody 

 and more or less lignified fibre of hay, and does not become 

 fully developed in the grain until the grain has become ripe. 

 True ripening of the grain takes place only after more or less 

 of the original moisture of the grain has been given off. The 

 abundant presence of this enzyme in good oats furnishes us 

 with an explanation of the great rapidity with which the 

 contents of these grains become broken up in the early stages 

 of digestion, and confirms the high estimation in which oats 

 are held as a food for horses ; for without this enzyme a con- 

 siderable portion of the flour of the oats would be unaffected 

 by the gastric and pancreatic juices, and would enter the 

 caecum undigested. "The animal itself, besides affording a 



