COMPOSITION AND CHARACTERS OF URINE 1121 



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 acid 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-chloroform 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 intestines by the action of 

 micro-organisms on bile pigment. 



Other pigments which may occur in urine are uroerythrin and hsema- 

 toporphyrin. Uroerythrin gives the pink colour to urate sediments. Its 

 chemical nature is not known. It is distinguished by the fact that on 

 addition of 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 in the form of alkaline hsematopor- 

 phyrin and gives the characteristic absorption bands of the latter. 



Urorosein is a name that has been given to a pigment which is formed 

 when the urine is treated with strong mineral acids. It is probably an 

 indol derivative. It gives a single absorption band between the lines 

 D and E. 



ABNORMAL CONSTITUENTS OF THE URINE 



A very large number of substances occur in the urine in minute traces and may be 

 detected when large quantities of this fluid are worked up at one time. Most of the so- 

 called pathological constituents may be detected in this way in normal urine. It is 

 only when they occur in easily detectable amounts that their presence becomes of any 

 significance. 



COAGULABLE PROTEIN. Under normal circumstances urine is free from any 

 coagulable protein except the small traces of mucinous material, nucleoprotein, which 

 gives the cloudiness to the urine. If the kidney-cells are damaged by disease, by inter- 

 ference with their blood-supply, or by circulating poisons, the glomerular epithelium 

 permits the passage of a certain amount of the proteins of the plasma. Under these 

 circumstances, if small pieces of the kidney be plunged into boiling water, the coagulated 

 protein may be seen in Bowman's capsule. The presence of coagulable protein (gene- 

 rally spoken of as albumin) in the urine is significant of the pathological conditions of 

 the kidney associated with Bright's disease. A small trace will generally be found in 



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