274 FUNCTIONS OF THE BILE. 



and baptisin, act with considerable power both on the liver and the intestinal glands. Cala- 

 bar bean stimulates the liver, and the increased secretion caused thereby may be reduced by 

 sulphate of atropin, although the latter drug, when given alone, does not notably affect the 

 secretion of bile. The injection of water or bile slightly increases the secretion. In all cases 

 where purgation was produced by purely intestinal stimulants, such as magnesium sulphate, 

 gamboge, and castor oil, the secretion of bile was diminished. In all such experiments it is most 

 important* that the temperature of the animal be kept up, else the secretion of bile diminishes. 

 Paschkis's results on dogs differ considerably from those of Rutherford. He asserts that only 

 the bile-acids (salts) of all the substances he investigated excite a prompt and distinct chola- 

 gogue action.] 



[As yet we cannot say definitely whether, or not, these substances stimulate the secretion of bile, 

 by exciting the mucous membrane of the small intestine, and thereby inducing reflex excitement 

 of the liver. Their action does not seem to be due to increase of the blood-stream through the 

 liver. More probably, as Rutherford suggests, these drugs act directly on the hepatic-cells or 

 their nerves. Acetate of lead directly depresses the biliary secretion, while some substances 

 affect it indirectly.] 



[Cholesteraemia. Flint ascribes great importance to the excretion of cholesterin by the bile, 

 with reference to the metabolism of the nervous system. Cholesterin, which is a normal in- 

 gredient of nervous tissue, is excreted by the bile ; and if it be retained in the blood "choles- 

 teraemia," with grave nervous symptoms, is said to occur. This, however, is problematical, 

 and the phenomena described are probably referable to the retention of the bile-acids in the 

 blood.] 



181. FUNCTIONS OF THE BILE. [(1) Bile is concerned in the digestion of 

 certain food-stuffs ; (2) part is absorbed ; (3) part is excreted.] 

 (A) Bile plays an important part in the absorption of fats : 



(1) It emulsio?iises neutral fats, whereby the fatty granules pass more readily 

 through or between the cylindrical epithelium of the small intestine into the lac- 

 teals. It does not decompose neutral fats into glycerine and a fatty acid, as the 

 pancreas does ( 170, III.). 



When, however, fatty acids are dissolved in the bile, the bile-salts are decomposed, the bile- 

 acids being set free, while the soda of the decomposed bile-salts readily forms a soluble soap 

 with the fatty acids. These soaps are soluble in the bile, and increase considerably the emulsi- 

 fying power of this fluid. Bile can dissolve fatty acids to form an acid fluid, which has high 

 emulsionising properties (Steiner). Emulsification is influenced by a 1 per cent, solution of 

 NaCl, or Na 2 S0 4 . 



(2) As fluid fat flows more easily through capillary tubes moistened with bile, it 

 is concluded that, when the pores of the wall of the small intestine are moistened 

 with bile, the fatty particles pass more easily through them. 



(3) Filtration of fat takes place through a membrane moistened with bile or bile- 

 salts under less pressure than when it is moistened with water or salt solutions (v. 

 Wistinghausen). 



(4) As bile, like a solution of soap, has a certain relation to watery solutions, as 

 well as to fats, it permits diffusion to take place between these two fluids, as the 

 membrane is moistened by both fluids. 



It is clear, therefore, that the bile is of great importance in the absorption of fats. This is 

 strikingly illustrated by experiments on animals, in which the bile is entirely discharged exter- 

 nally through a fistula. Dogs under these conditions, absorbed at most 40 per cent, of the fat 

 taken with the food [60 per cent, being given off by the faeces, while a normal dog absorbs 99 

 per cent, of the fat]. The chyle of such animals is very poor in fat, is not white but trans- 

 parent ; the faeces, however, contain much fat, and are oily ; the animals have a ravenous 

 appetite ; the tissues of the body contain little fat, even when the nutrition of the animals has 

 not been much interfered with. Persons suffering from disturbances of the biliary secretion, or 

 from liver affections, ought, therefore, to abstain from fatty food. [The digestion of flesh and 

 gelatin is not interfered with in dogs by the removal of the bile (v. Voit).] 



(B) Fresh bile contains a diastatic ferment, which transforms starch into sugar, 

 and also glycogen into sugar. 



(C) Bile excites contractions of the muscular coats of the intestine, and con- 

 tributes thereby to absorption. 



(1) The bile-acids act as a stimulus to the muscles of the villi, which contract from time to 

 time, so that the contents of the origins of the lacteals are emptied towards the larger lym- 



