FOOD VALUE OF CELLULOSE 203 



lose undergoes in the intestine and in which it is broken down 

 into CH 4 , CO 2 and volatile fatty acids (acetic acid, isobutyric 

 acid, valerianic acid). Hitherto marsh-gas fermentation of 

 cellulose has been usually regarded as about equalled by its 

 hydrogen fermentation. From recent investigations, ema- 

 nating from the laboratory of N. Zuntz 39 (in which the gases 

 of fermentation were obtained directly by puncture from the 

 digestive apparatus of a goat, in which the paunch was 

 sutured into a wound of the abdominal wall) it is apparent, 

 however, that the hydrogen of the total fermentation gases 

 never amounts to more than 10 per cent, of the methane 

 found with it. Under normal circumstances it would appear 

 that the CH 4 fermentation preponderates to a marked de- 

 gree, at least as long as the reaction of the fermenting mix- 

 ture is acid. A simple chemical formulation of this fermen- 

 tation process is at the present out of the range of possibility. 

 The part of the tract in which food rich in cellulose is prin- 

 cipally broken up is in ruminants in the proventricle 

 (paunch) ; in other herbivora with single-chambered stom- 

 ach, as the horse and rabbit, an analogous role is to be as- 

 signed probably to the highly developed caecum in handling 

 cellulose. 31 In man the colon seems to be the part concerned 

 in cellulose digestion. 32 



Food Value of Cellulose. This brings us to the main 

 point at issue has cellulose or its fermentation products a 

 real value as a nutrient? 33 A number of physiologists 

 especially interested in metabolism have absolutely denied 

 this view, as Weiske, who experimented upon a sheep, and 

 E. Wolff, who worked on a horse ; while others, as Knieriem, 

 Kellner, 34 and recently Ellenberger and Scheunert, take the 



" J. Markoff (N. Zuntz's Lab., Berlin), Biochem. Zeitschr., 34, 211, 1911. 



a N. Zuntz, Verb. d. Berlin, physiol. Ges., March 10, 1905; Centralbl. f. 

 Physiol., 19, 581-, 1905; W. Ustjanzew (Zuntz'3 Lab.), Biochem. Zeitschr., 4, 

 154, 1907. 



32 F. Schilling, Arch. f. Verdauungskr., 16, 720, 1910. 



33 Cf. W. Biedermann, Handb. d. vergl. Physiol., p. 1336, 1911. 



**O. Kellner, Die Ernahrung d. landwirtschaftl. Nutztiere, Berlin, Parey, 

 1906. 



