12 BILIN. 



constitution of taurin can be best understood by remembering how it is 

 obtained synthetically, viz., by subjecting ammonic isethionate (NH 4 , C 2 H 5 , 

 SO 4 ) to a high temperature, in consequence of which it loses the elements of 

 a molecule of water. Neither the origin nor the destiny of Taurin in the 

 organism is known. It was, until lately, supposed that it was represented 

 in the urine by sulphates, and that its amide took part in the constitution of 

 urea ; but it has been recently proved experimentally that when dogs are 

 fed with Taurin, that body leaves the organism partly as such, but chiefly in 

 the form of Tauro-carbamic acid (C 3 H 8 N a O 4 ). 



Cholalic Add (C 24 H 40 O 5 ) is insoluble in water, very soluble in alcohol, 

 sparingly in ether. It crystallizes from its solution in dilute alcohol, in 

 tetrahedra or octahedra, which, at first transparent, soon become opaque on 

 exposure. At high temperatures, it loses H 2 O and yields dyslysin (C 24 H L6 

 O 3 ) and undergoes a similar change when boiled with hydrochloric acid. It 

 is contained in decomposed bile as alkaline cholalate, and is precipitated 

 therefrom on the addition of acetic acid. From this precipitate it can be 

 extracted by alcohol. 



Bilimbin (Cholepyrrhin C 32 H 36 N 4 O 6 ) can be obtained directly from human 

 bile, or from that of the dog by shaking it with chloroform. On separating 

 the solution thus obtained from the bile and then distilling off the chloroform, 

 a pitchy residue is left, which, after it has been exhausted by alcohol, is found 

 to contain crystals of bilirubin. The alcohol contains cholesterin and a brown 

 colouring matter which has been called bilifuscin. Bilirubin is a principal 

 constituent of biliary calculi ; powdered gall stone is first extracted with ether 

 to remove the cholesterin, and then treated with dilute hydrochloric acid and 

 washed : the residue yields, when treated with chloroform, a yellowish-brown 

 solution, from which bilirubin is precipitated on the addition of alcohol, or 

 crystallizes on evaporation, in red needles. It is insoluble in water, nearly 

 insoluble in boiling alcohol and in ether, more soluble in bisulphuret of carbon, 

 and most of all in chloroform. Its solution shows no absorption bands. It 

 further dissolves readily in potash or soda, and when the alkaline solution is 

 exposed to air, it gradually becomes green, and gives, when treated with 

 hydrochloric acid, a green precipitate (biliverdin), which is insoluble in chloro- 

 form but soluble in alcohol. Bilirubin, in dilute alkaline solution, when acted 

 on by sodium-amalgam, yields Maly's Hydro-bilirubin, a red body insoluble in 

 water, of which the solution in absolute alcohol shows before the spectroscope a 

 broad absorption band, between E and F. It is supposed by its discoverer to 

 be identical with the colouring matter of faeces (stercobolin) and with the 

 urobilin of Jaffe, from both of which, however, it differs in some particulars. 

 The physiological origin and destiny of the colouring matter in the bile is 

 known. It has been observed that when crystalline haemoglobin in solution 

 is injected into the circulation, the rate at which colouring matter is secreted 

 by the liver increases enormously, and that bile pigment appears in the urine. 

 In the intestines most of the bilirubin secreted is converted into stercobilin 

 and discharged, but the chemical relations between it and the excreted colour- 

 ing matters are as yet uncertain. Liquids which contain bilirubin change 

 colour on the addition of nitric acid containing a trace of nitrous acid : at first 

 green, the colour passes through blue, violet and red, finally fading into 



