1903.] PUBLIC DOCUMENT — No. 33. 81 



although these quantities are removed from the digestive 

 tract, it is by no means certain that tliey have a food value 

 equal to starch and similar substances. Considerable <]uan- 

 tities have been recojjnized in the urine of human beinirs. 

 AVeiske and Wicke,^ as well as ourselves, liave recognized 

 only ti'aces in the urine of sheep. It has been assumed that 

 they may be destroyed in the digestive tract by various 

 micro-organisms. Tollens'^ very pertinently suggested that 

 they were no less susceptible to such destructive influences 

 than is starch. 



It remained, however, for Kellner,^ as a result of very 

 exhaustive experiments with the aid of the respiration 

 calorimeter, to furnish definite information. Oxen were fed 

 a basal ration, to which were added at different times 2.5 

 kilograms of starch and 3 kilograms of rye straw, the latter 

 previously extracted with dilute sodium hj^drate under pres- 

 sure. He found 2.32 per cent, of the carbon from the 

 digested starch to be in the form of marsh gas (equivalent 

 to a loss of 10.1 per cent, potential energy) ; and, from the 

 extracted straw^ digested, 3.34 per cent, of the carbon to be 

 in the form of marsh gas (equal to a loss of 14 per cent, of 

 potential energy) . The diflerences were not marked. In 

 general, the poorer the mechanical condition of the feed and 

 the larger the amount of incrusting substance present, the 

 longer it remains in the intestines and the greater the oppor- 

 tunity for micro-organisms to attack it ; and, vice versct^ the 

 more easily digested starchy matters, free from lignin, are 

 more quickly resorbed and are less likely to undergo bacterial 

 destruction. Kellner concluded that the furfural-yielding 

 substances (pentosans) of the extracted straw took part in 

 the formation of fat, and indirectly in the formation of flesh, 

 to as great an extent as did either starch or cellulose.^ 



It may be safely concluded, therefore, that the pentosans 

 are as digestible as any of the other fodder groups (except 

 in the presence of excessive incrusting substance), and that 

 the digested material is practically utilized in the animal 

 organism to the same degree as the other carbohydrates. 



* Loco citato. ^ Journal f. Landw., 1897, p. 110. '' Loco citato, pp. 426-428. 



* This treated straw contained 82 per cent, of crude fibre, and over 30 per cent, 

 of pentosans. ^ Loco citato, p. 457. 



