FUNCTIONS OF THE BlLE. 365 



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 by covering it with cotton wool, else the secretion of bile diminishes. 



As yet, we cannot say definitely whether these substances stimulate the secretion 

 of bile, by exciting the mucous membrane of the duodenum or other part 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 pro- 

 bably, 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.] 



Cholestersemia. 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 ingredient of nervous-tissue, is excreted by the bile ; and if it be 

 retained in the blood, "cholestersemia," 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 of it is absorbed; 



(3) part is excreted.] 



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



(1.) It emulsionises neutral fats (170, III.), whereby the fatty granules 

 pass more readily through or between the cylindrical epithelium of 

 the small intestine into the lacteals. It does not decompose neutral 

 fats into glycerine and a fatty acid, as the pancreas does. 



When, however, fatty acids are dissolved in the bile (Lenz) 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 emulsifying power of this fluid. Bile can 

 dissolve directly fatty acids to form an acid fluid, which has high enmlsionising 

 properties (Steiner). 



(2.) As fluid fat flows more rapidly through capillary tubes when they 

 are moistened with bile, it is concluded that when the pores of the 

 absorbing 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 (v. 

 Wistinghausen) . 



It is clear, therefore, that the bile is of great importance in the preparation and 

 in the absorption of fats. This is forcibly illustrated by experiments on animals, 

 in which the bile is entirely discharged externally through a fistula. Dogs, under 

 these conditions, absorbed at most 40 p.c. of the fat taken with the food (v. Voit). 



