254 DIGESTION. [CHAP. xxv. 



According to Berzelius' s view of the composition of bile, its essen- 

 tial and most important constituent is the Bilin, a substance which 

 has a remarkable tendency, under certain circumstances, to be 

 metamorphosed into taurine,hydrochlorate of ammonia, and into two 

 resinous acids, which he has named /W^ntc acid and cholinic acid. 



Bilin is inodorous, and has a peculiar sweetish-bitter taste, most 

 perceptible at the base of the tongue and fauces. This sweetness 

 is attributed by Berzelius to the admixture of some glycerin, which 

 may be derived from the fatty matters of the bile. It dissolves 

 readily in water and in alcohol, but not in ether. It is neutral, 

 and forms soluble combinations with acids and bases. 



The substances above-named may be obtained from bilin by 

 digesting it in dilute hydrochloric acid. The fellinic and cholinic 

 acids are insoluble, the others are soluble, in water. 



Taurin is a crystalline substance, consisting of colourless six- 

 sided prisms. It dissolves in about sixteen times its weight of 

 water at 60, and is more soluble at a higher temperature. It 

 contains sulphur according to Redtenbacher.* Its composition is 

 represented by the formula C 4 N 2 H 4 O 6 S 2 . The fellinic and cholinic 

 acids resemble each other very much in their external properties. 

 They are little or not at all soluble in water, but are readily dis- 

 solved by alcohol ; the fellinic acid is readily dissolved by ether, the 

 cholinic only slightly. They form nearly similar compounds with 

 the alkalies, earthy and metallic oxides ; but their salts of baryta 

 differ ; the fellinate of baryta being soluble in alcohol, the cholinate 

 of baryta insoluble. The product called by Berzelius dyslysin is 

 obtained by boiling these acids for a long time in hydrochloric 

 acid. It is dissolved with difficulty in boiling alcohol, and on cool- 

 ing precipitates an earthy powder. Fellinic and cholinic acids have 

 the property of combining and forming acid compounds with unde- 

 composed bilin \ these have been named by Berzelius, bili-fellinic 

 and l)ili- cholinic acids. 



According to Berzelius and Mulder, bilin begins to undergo these 

 changes in the gall-bladder of the living animal ; and it is, probably, 

 this proneness to change, on the part of its principal constituent, 

 which makes the analysis of bile so difficult, and gives rise to so 

 much diversity of opinion among chemists. 



The fat of bile exists partly in combination with soda, as oleate 

 and margarate of soda, and principally as a peculiar substance 

 found only in bile and in the nervous matter, namely, cholesterine. 

 This is separable from the other constituents of bile by agitation 



* Annalen der Chemieund Pharmacie von Liebig und Wohler, Feb., 1846. 



