264 DIGESTIVE SYSTEM. 



foregoing, but often quite as hypothetical, makes the bile to 

 consist of a fluid which opposes the putrid fermentation of 

 the contents of the intestine; indeed, when the bile is turned 

 out of its course, and made to flow outwards, the faeces are 

 found to acquire a very fetid odor. The bile is also sometime^ 

 supposed to be an excitant of the mucous and of the intestinal 

 muscle; we have seen, however, that the erectile action of the 

 villi belongs entirely to the epithelium, and takes place long 

 before the arrival of the bile, under the exciting influence of 

 the gastric juice alone : while, on the other hand, changing 

 the natural course of the bile out of the intestine produces 

 no effect on the motion of the muscular coats of this canal. 



We take, finally, for our starting-point, the fact that the 

 bile enters the intestine only when the process of absorption 

 is nearly completed, and when the epithelium which has 

 served for its passage, begins to decay and desquamate. 

 The bile itself then appears to undergo several changes : its 

 coloring matter is precipitated, and mixes with the faeces, 

 imparting its own color to them ; the case is the same in 

 regard to the cholesterine, which is an excrementitial prod- 

 uct ; the remainder of the bile seems to disappear in the 

 intestinal walls, and to become reabsorbed, not in its simple 

 form, however, for none of its acids are found in the blood : 

 it appears to be decomposed in the very act of penetrating 

 the intestinal mucous coat. 



This assemblage of facts, including the well-known one 

 that the bile speedily dissolves all cellular elements (as may 

 be easily observed in the blood globules), beside the circum- 

 stance that the greatest activity of the epithelial desquama- 

 tion of the intestine takes place when it comes in contact 

 with the bile; all justify us in concluding that the exudation 

 and the action of the bile have some relation to this decay 

 of the epitheliums. The chief purpose served by the bile is 

 thus the renewal of the cellular coats, promoting the decay 

 of the old elements, and the restoration of the new : if we 

 may be allowed the expression, it sweeps the workshop clean, 

 in which the laborious task of absorption has just been com- 

 pleted, and forms new epithelial organs ready to begin the 

 process over again. This reconstitution takes place by 

 means of the fresh cells which exist in the deeper portion 

 of the epithelium. The intestine is, thus, never unprovided 

 with epithelial cells; the new generation takes place so 

 rapidly that it is impossible to distinguish it, half-hidden as 

 it is by the ruins of former cells. We have seen that when 



