EXPERIMENTS ON DIGESTION. 
587 
always found in the small intestines. It is, nevertheless, possible 
that a portion of these bubbles may proceed from the decomposition 
of the food. If the chyle contains little or even no hydrochloric 
acid, but only free acetic acid, this will equally transform the car- 
bonate of soda of the bile into an acid. In fact, the mixture of the 
chyle and the bile will always contain some free acid, but generally 
that will be acetic acid without hydrochloric acid, because this last 
will precipitate the albumen of the pancreatic juice. 
2. The free acid of the chyme precipitates the mucus of the bile 
in the state of a coagulum. This last draws with it a great part of 
the colouring principle of the bile, for the precipitated mucus has 
a brown colour. The cholesterine is also precipitated, since we have 
often obtained a certain quantity of this substance when treating 
with alcohol the insoluble portion of the matter contained in the 
small intestine. 
The margaric acid, which we have found in the intestinal canal, 
proceeds probably from the bile, and it had been separated from 
the carbonate of soda of this fluid by the hydrochloric acid. As 
we ordinarily extract from a portion of the insoluble contents of 
this water a resin which possesses the same properties as the 
biliary resin, we do not hesitate to consider it as such, and to 
think that it contributes to the formation of the excrement. We 
have found it in a state of solution when the fluid of the inferior 
portion of the small intestine was alkaline, as in a horse that had 
fasted before it was killed. It is totally or in a great part rejected 
with the excrement, and it appears to be a substance of which 
the intestines hasten to free themselves. 
The colouring principle is not entirely precipitated, as is proved 
by the yellow or brown colour which the fluids obtained by the 
filtration of the contents of the small intestine always exhibit. 
It does not appear, however, to be absorbed in that state of solution, 
for the colour of the filtered fluids becomes deeper in proportion 
as the contents of the intestine descend in the canal. It is, then, 
like the resin, expelled entirely with the excrement, in part com- 
bined with the intestinal mucus, and in part in a fluid form. 
Physiologists generally assert that the mixture of the acid 
chyme with the bile determines the separation of the chyle, and 
its precipitation under the form of flocculi. This hypothesis, how- 
ever, is certainly false. The circumstance alone of the absorption 
of the chyle which demands that it shall be fluid, renders it alto- 
gether improbable that it can be separated in flocculi, that is to 
say, under another form than that of a liquid, and in the very 
place where the absorption is effected. Besides, the experiments 
which we have made on the mixture of the fluid contained in the 
stomachs with bile, both when cold and at a moderate heat, and in 
