USES OF THE BILE. 555 



stances which, unlike the urea and uric acid of the renal excretion, do 

 not pre-exist in the blood, but are formed in the hepatic cells. Sec- 

 ondly, the bile, as already stated (p. 538), is much more abundantly 

 secreted during the process of digestion than at any other period ; 

 and although this may be due to the accompanying activity of the 

 portal circulation, yet the general adaptation of means to ends in the 

 animal economy, suggests the conclusion that the secretion is most re- 

 quired at that particular time. Lastly, the situation at which the bile 

 is discharged into the alimentary canal, immediately below the stom- 

 ach, and therefore very high up in the intestine, seems to indicate its 

 special adaptation to the further digestion of some important constitu- 

 ent of the chyme. Nevertheless, as we shall hereafter see, a large 

 portion of the solid constituents of the bile is removed from the body, 

 and this fluid must, to a great extent, be regarded as an excrementi- 

 tious fluid, serving to eliminate carbon, hydrogen, and sulphur. The 

 bile also serves certain supplementary non-chemical uses. Thus, it 

 excites the mucous membrane of the intestine, and so probably causes 

 an increased secretion of mucus and intestinal juice. It moreover 

 stimulates, either directly or through the nerves, the contractile fibre- 

 cells of the mucous membrane and its villi, as well as those of the 

 muscular coat of the intestine ; the former action, probably, promotes 

 absorption by the villi; whilst the latter excites the intestinal peri- 

 staltic action, and so aids in the onward movement of the intestinal 

 contents. It is well known that a scanty supply of bile may lead to 

 constipation, whilst an excess of that fluid induces diarrhoea : hence, 

 it may be inferred, that a proper quantity helps to maintain the 

 healthy action of the intestines. The inspissated bile of the ox is 

 used as an aperient medicine. 



As regards the chemical action of the bile, experiments, made out- 

 side the body, by digesting various constituents of food in that fluid, 

 at a temperature of 100, show that it has an exceedingly feeble ac- 

 tion in changing starch into sugar ; cane sugar is slowly converted by 

 it into lactic acid ; it neither dissolves albuminoid substances, nor 

 saponifies or dissolves fat. Albuminoid and gelatinoid bodies, al- 

 though stained, are otherwise unaltered ; fatty matters, agitated with 

 bile, form an imperfect opaque emulsion, but after a time, if left un- 

 disturbed, separate themselves entirely from that fluid, unchanged. 

 Bile is said to arrest the actions of saliva and gastric juice, even when 

 these have already commenced, upon starch and albuminoid substances. 

 Indeed, the bile and the gastric juice decompose each other, when 

 mixed out of the body; but this does not seem to be the case when 

 the gastric juice is already combined with peptone. In living animals, 

 in which biliary fistulas have been established, so that the bile, pre- 

 vented from entering the intestinal canal, escapes at the surface of 

 the body, amylaceous, albuminoid, and gelatinoid substances are still 

 completely digested. With regard to fatty matters, however, the 

 bile appears in some way to assist in, or to determine, their absorption. 

 It has been assumed that the bile is a saponaceous compound, and 

 that it Dissolves fatty matters directly, like an ordinary soap; but 

 soaps contain more or less free alkali, which assists in dissolving ad- 



