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 iikiy 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 Hofmeister, 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. /'. mikr. AnaL. Bonn, 1865, Bd. i. S. 203. 
2 Ztsdhr.f. Biol., Miinchen, 1884, Bd. xx. S. 52 ; ibid., 188S, Bd. xxiv. S. 105. 
3 Ztschr. f. physiol. Chem., Strassburg, 1886, Bd. x. S. 401. 
4 Arch./. wissensch. u. prakt. Thierh., Berlin. 1885, Bd. xi. S. 46. 
5 Bunge, "Physiological and Pathological Chemistry," 1894, p. 75. 
6 v. Knierieni. Ztschr. f. Biol., Miinchen, 1885, Bd. x.\i. S. 67. 
7 Grbger, Ztschr. f. ang. Chem., Berlin, 1889, S. 62. 
