1252 PHYSIOLOGY 



chloroform. It is important not to add too much chloride of lime, as otherwise 

 the blue colour first produced will be destroyed by further oxidation. 



THE URINARY PIGMENTS. Normal urine gives no definite 

 absorption bands. It owes its colour to the presence of a yellow pig- 

 ment, urochrome. In order to separate urochrome from urine, the 

 urine is saturated with crystals of ammonium sulphate and filtered. 

 The filtrate, which still contains nearly all the colour of the urine, is 

 shaken up with alcohol, which withdraws the greater part of the 

 colouring-matter. On concentrating the alcoholic solution and pour- 

 ing it into an equal volume of ether, an amorphous brown precipitate 

 falls, which is the urochrome. Urochrome, on treatment with alde- 

 hyde, yields a pigment closely similar to, if not identical with, urobilin. 

 On the other hand, urobilin, treated with potassium permanganate, 

 is converted into a substance practically identical with urochrome. 

 Urochrome must therefore be derived from the same source as urobilin. 



Urobilin is rarely present in normal urine, and then only in the form 

 of a chromogen, from which it must be set free by acidification. In 

 certain pathological conditions, especially in cirrhosis of the liver, 

 urobilin may occur in the urine in considerable quantities. In order 

 to extract urobilin from such urine, the urates are first precipitated 

 by saturation with ammonium chloride, and the filtrate is then 

 saturated with ammonium sulphate and a drop of sulphuric added. On 

 shaking the fluid up with a mixture of two parts ether and one part 

 chloroform, the urobilin is taken up by the latter. The ether-chloro- 

 form solution is separated off and shaken up with caustic soda, when 

 the urobilin passes entirely into the alkaline solution. 



Urobilin in solution gives a single absorption band between the 

 lines b and F, i.e. at the junction of the green and blue of the spectrum. 

 On treating with zinc chloride and ammonia its solutions show a 

 well-marked green fluorescence. The urobilin of urine is identical with 

 stercobilin, the colouring-matter of the faeces. It is formed from bile 

 when the latter decomposes, and is probably produced in the intes- 

 tines by the action of micro-organisms on bile pigment. 



Other pigments which may occur in urine are uroerythrin and 

 hsematoporphyrin. Uroerythrin gives the pink colour to urate sedi- 

 ments. Its chemical nature is not known. It is distinguished by the 

 fact that on addition of a caustic soda the pink colour is changed to 

 green. On suspending the red- coloured precipitate of urates in hot 

 water and extracting with amyl alcohol, a pink solution is obtained 

 which shows two absorption bands in the green part of the spectrum. 



Hcematoporphyrin is only present in very small amounts in normal 

 urine, but under certain conditions, especially after poisoning with 

 sulphonal, it may occur in such large quantities as to give the 

 urine a deep purple colour. Under these circumstances it is found 



