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CHEMICAL PROCESSES IN THE [NTESTINE. 511
cellulose undergoes a fermentation in the intestine by the action of micro-
organisms, producing marsh-gas, acetic acid, and butyric acid, has
been especially shown by Tappeiner; still it is not known to what extent
the cellulose is destroyed in this way. 1
The bile has, as shown by Moore and Rockwood 2
and then espe-
cially by Pfluger, the property to a high degree of dissolving fatty
acids, especially oleic acid, which itself is a solvent for other fatty acids,
and hence, as will be seen later, it is of great importance in the absorp-
tion of fat. It is also of great importance that the bile, as previously
stated, not only activates the steapsinogen, but that, as first shown by
Nencki and Rachford,3
it accelerates the fat-splitting action of the
steapsin. According to v. Furth and Schutz 4
the bile-salts are the
active constituents of the bile in this cleavage, and the fatty acids set
free can combine with the alkalies of the intestinal and pancreatic juices
and the bile, producing soaps which are of great importance in the
emulsification of the fats.
If to a soda solution of about 1-3 p. m. pure, perfectly neutral
olive-oil is added in not too large a quantity, a transient emulsion is
obtained after vigorous shaking. If, on the contrary, one adds to the
same quantity of soda solution an equal amount of commercial olive-
oil (which always contains free fatty acids), the vessel need only be
turned over for the two liquids to mix, and immediately there appears
a very finely divided and permanent emulsion, making the liquid appear
like milk. The free fatty acids of the commercial oil, which is always
somewhat rancid, combine with the alkali to form soaps which act to
emulsify the fats (Brucke, Gad, Loewenthal 5
). This emulsifying
action of the fatty acids split off by the pancreatic juice is undoubtedly
assisted by the habitual occurrence of free fatty acids in the food, as
well as by the splitting off of fatty acids from the neutral fats in the
stomach (see page 476).
Bile completely prevents peptic zymolysis in artificial digestion,
l
On the digestion of cellulose see Henneberg and Stohmann, Zeitschr, f. Biologie,
21, 613; v. Knieriem, ibid., 67; Hofmeister, Arch. f. wiss. u. prakt. Thierheilkunde,
11; Weiske, Zeitschr. f. Biologie, 22, 373; Tappeiner, ibid., 20 and 24; Mallevre,
Pfliiger’s Arch., 49; Omeliansky, Arch. d. scienc. biol. de St. Petersbourg, 7; E. Muller,
Pfliiger’s Arch., 83; Lohrisch, Zeitschr. f. physiol. Chem., 47 (literature); Pringsheim,
ibid. 78, 266 (1912).
2
Proceedings of Roy. Soc, 60, and Journ. of Physiol., 21. In regard to Pfliiger’s
work see Absorption.
3
Nencki, Arch. f. exp. Path. u. Pharm., 20; Rachford, Journal of Phvsiol., 12.
4
Centralbl. f. Physiol., 20.
* Brucke, Wien, Sitzungsber., 61, Abt. 2; Gad, Arch. f. (Anat. u.) Physiol., 1878;
Loewenthal, ibid., 1897.
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