ITS FUNCTIONS. 103 



effected in these substances till the putrefactive process is set up 

 by the biliary mucus. On the other hand, the water effused with 

 the bile must not be disregarded as a solvent for the soluble 

 portions of the chyme ; we have already seen that the blood of the 

 hepatic veins is always much poorer in water than that of the portal 

 vein, and that the latter fluid often contains an extraordinary quantity 

 of water ; this water must necessarily often circulate from the intes- 

 tinal veins into the portal vein, and from it, through the biliary 

 ducts, back into the intestine, and must thus the more contribute 

 to the gradual separation and extraction of the chyme, in conse- 

 quence of its again losing in the intestine the substances it had 

 taken up from the liver, owing to the insolubility of the biliary 

 acids. This water is therefore differently freighted, according as it 

 flows from the liver to the intestine, or from the intestine to the 

 liver ; or, so to speak, it percolates two different filters, each of 

 which is only permeable for certain substances. 



Moreover, it has been attempted to show that the bile exerts 

 a general chemical action on the contents of the intestine, but 

 these enquiries have led to directly opposite views. Some have 

 considered that the bile exerts an antiseptic action on those con- 

 stituents of the intestinal canal which have a tendency to decom- 

 position ; while others, again, ascribe to the bile the property of 

 imparting a definite direction to the metamorphosis of these sub- 

 stances by its own decomposition. To those who would rest 

 satisfied with such general views of the subject, we may observe, 

 that the first of these opinions is, at all events, untenable ; pure bile 

 may certainly exert an antiseptic action on substances which 

 become readily decomposed, as flesh, &c. ; the bile, however, which 

 is effused into the intestinal canal is not pure, but is mixed with 

 mucus, which very readily undergoes decomposition, and, in point 

 of fact, is actually decomposed in the intestine, as may be seen by 

 the simplest observation. Hence we might, perhaps, be supposed 

 to concur in the second view, according to which a definite ha- 

 racter is impressed upon the metamorphosis of the food by the 

 bile as a special ferment. But it must be frankly confessed that 

 the assumption of fermentative actions in any process is nothing 

 more than an indication of our positive ignorance. We shall, 

 therefore, now proceed to the more special investigation of the 

 metamorphoses which the individual constituents of the chyme 

 undergo in consequence of the action of the bile. 



We must by no means overlook the circumstance that the 

 intestinal contents, when no bile is mixed with them, very soon 



