CONSTITUENTS OF THE BILE. 267 



e.g., potassic chloride, but it retains the vegetable alkaloids, provided they are not present in 

 too large an amount in the blood. The ptomaines are similarly retained in the liver. The 

 liver possesses this property only as long as it contains glycogen {H. Eogers).} 



177. CONSTITUENTS OF THE BILE. Bile is a yellowish-brown or dark 

 green coloured transparent fluid, with a sweetish, strongly bitter taste, feeble musk- 

 like odour, and neutral reaction. The specific gravity of human bile from the gall 

 bladder= 1026 to 1032, while that from a fistula- 1020 to 1011. It contains : 



(1) Mucus, which gives bile its sticky character, and not unfrequently makes it 

 alkaline ; it is the product of the mucous glands and the goblet-cells of the mucous 

 membrane of the larger bile-ducts. When bile is exposed to the air, the mucus 

 causes it to putrefy rapidly. It is precipitated by acetic acid, or alcohol. 



[The bile formed in the ultimate bile-ducts does not seem to contain mucin or mucus, but 

 bile from the gall-bladder always does. It is formed by the mucous glands in the larger bile- 

 ducts ( 178).] 



(2) The Bile-Acids. Glycocholic and taurocholic acids, so-called conjugate acids, 

 are united with soda (in traces with potash) to form glycocholate and taurochol- 

 ate of soda, which have a bitter taste, and rotate the plane of polarised light to the 

 right. In human bile (as well as in that of birds, many mammals, and amphi- 

 bians) taurocholic acid is most abundant ; in other animals (pig, ox) glycocholic acid 

 is most abundant but is absent in sucklings. 



(a) Glycocholic acid, C 26 H 43 N0 6 ; when boiled with caustic potash, or baryta 

 water, or with dilute mineral acids, it takes up H 2 and splits into 



Glycin ( = Glycocoll = Gelatin Sugar = Amido-acetic acid) = C 2 H 5 lSr0 2 . 



+ Cholalic acid (also called Cholic acid) . . = C 24 H 40 O 5 . 



= Glycocholic acid + Water '. '. = C 26 H 43 N0 6 + H 2 0. 



(b) Taurocholic acid, C 26 H 45 NS0 7 , when similarly treated, takes up water and 

 splits into 



Taurin ( = Amidorethyl-Sulphuric acid) = C 2 H 7 NS0 3 . 

 + Cholalic acid = CL,ILnO K . 



= Taurocholic acid + Water . . = C 26 H 45 NS0 7 + H 2 {Strecker). 



[Solutions of taurocholic acid are antiseptic, and if sufficiently strong interfere with the de- 

 velopment of bacteria, and prevent the alcoholic and lactic fermentations, as well as the tryptic 

 and diastatic action of the pancreas (Umich).] 



Preparation of the Bile-Acids. Evaporate bile to \ of its volume, rub it up into a paste with 

 excess of animal charcoal, and dry at 100 C. Extract the black mass with absolute alcohol, 

 and filter. After a part of the alcohol has been removed by distillation, the bile-salts are pre- 

 cipitated in a resinous form, and on the addition of excess of ether, there is formed immediately 

 a crystalline mass of glancing needles (Platner's "crystallised bile "). The alkaline salts of 

 the bile-acids are freely soluble in water or alcohol, and insoluble in ether. Neutral lead acetate 

 precipitates the glycocholic acid as lead glycocholate from the solution of both salts ; the 

 precipitate is collected on a filter, dissolved in hot alcohol, and the lead is precipitated as lead 

 sulphide by H 2 S ; after removal of the lead sulphide, the addition of water precipitates the 

 isolated glycocholic acid. If, after precipitating the lead glycocholate, the filtrate be treated 

 with basic lead acetate, a precipitate of lead taurocholate is formed, from which the acid may 

 be obtained in the same way as described above {Strecker). 



With regard to the decomposition products of the bile-acids, glycin, as such, 

 does not occur in the body, but only in the bile in combination with cholic acid, in 

 urine in combination with benzoic acid, as hippuric acid, and lastly, in gelatin in 

 complex combination. 



Cholalic acid rotates the ray of polarised light to the right, and its chemical 

 composition is unknown. It is insoluble in water, soluble in alcohol, but soluble 

 with difficulty in ether, from which it separates in prisms. Its crystalline alkaline 

 salts are readily soluble in water. It is coloured blue by iodine, and occurs free 

 only in the intestine. 



Cholalic acid is replaced in the bile of many animals by a nearly related acid, e.g., in pig's 

 bile, by hyo-cholalic acid {Strecker) ; in the bile of the goose, cheno-cholalic acid is present 

 {Marsson, Otto). 



