A CTION OF INTESTINAL BA CTERIA ON FA TS. 471 



of the intestine possess the function, by means of a ferment, of dissolving 

 the cellulose ; this may be so, but no such ferment has ever been shown 

 to exist. Bunge supports his suggestion by analogy with the action 

 of some unicellular organisms on cellulose. 1 



Exposed to the action of certain organisms, cellulose undergoes 

 fermentation with the setting free of marsh gas (CH 4 ), and the forma- 

 tion of acetic and butyric acids ; how much of the altered cellulose goes 

 in this way in the digestive process is unknown. Tappeiner 2 tested 

 the action of the intestinal bacilli on cotton-wool, by soaking this in a 

 1 per cent, solution of bouillon and inoculating with the bacilli. Fer- 

 mentation with development of gas commenced, and there were formed 

 in the solution free fatty acids (up to and including valerianic acid), 

 while the cotton-wool nearly all dissolved. The gases set free were 

 marsh gas and carbon-dioxide. The nature of the products varies with 

 the organism acting on the cellulose ; thus Hoppe-Seyler 3 obtained the 

 same gases accompanied by a dextrin-like substance, by the action of 

 pond bacteria on cellulose in the form of filter paper, but did not observe 

 the formation of any fatty acids. 



Experiments on the artificial digestion of cellulose in the form of 

 new hay were made by Hofrneister, 4 who showed that the intestinal 

 juices of the horse were capable of dissolving nearly 80 per cent, of this 

 material. No formation of sugar but some fermentation and develop- 

 ment of gas were observed. 



The most important uses of cellulose lie, however, not in its value 

 as a nutrient foodstuff, but in giving bulk and looseness to the food and 

 in mechanically inducing peristalsis by irritation of the intestine. 5 For 

 this reason cellulose becomes an absolute necessity for animals with a 

 long intestine, such as the herbivora. Eabbits fed on food free from 

 cellulose rapidly die from intestinal inflammation ; but if the same food 

 be mixed with such an inert substance as horn shavings, nutrition goes 

 on quite normally, and the animals continue in perfect health, although 

 the horn shavings remain entirely unaltered. 6 The carnivora with their 

 short intestine require no such aid to peristalsis ; but in animals in an 

 intermediate position, such as man, bulky or cellulose-containing food, 

 while not indispensable, is from a dietetic point of view exceedingly 

 desirable. 



Action of the intestinal bacteria on fats. Under a normal con- 

 dition of the intestine, it is probable that very little decomposition of 

 the fats by bacteria takes place, but under abnormal conditions, such 

 as the absence of the bile or pancreatic juice, they are almost completely 

 decomposed into fatty acids, which pass out unabsorbed along with the 

 faeces. The first action of bacteria on fats consists in setting free the 

 corresponding fatty acids ; these are afterwards partially broken down 

 into mixtures of fatty acids lower in the series. 7 



Lecithins undergo a similar decomposition by bacteria under anae- 

 robic conditions ; they at first are split up into glycerophosphoric acid, 

 fatty acids, and choline. Afterwards, the choline is decomposed with 



1 E.g., Vampyrella ; Cienkowski, Arch. f. mikr. AnaL, Bonn, 1865, Bd. i. S. 203. 

 3 Ztsclir. f. Biol, Mlinchen, 1884, Bd. xx. S. 52 ; ibid., 1888, Bd. xxiv. S. 105. 



3 Ztsclir. f. physiol. Chem., Strassburg, 1886, Bd. x. S. 401. 



4 Arcli.f. wissensch. u. prakt. Thicrh., Berlin, 1885, Bd. xi. S. 46. 



5 Bunge, "Physiological and Pathological Chemistry," 1894, p. 75. 



6 v. Knieriem, Ztsdir. f. Biol., Miinchen, 1885, Bd. xxi. S. 67. 



7 Groger, Ztsclir. f. ang. Chem., Berlin, 1889, S. 62. 



