134 PRACTICAL PHYSIOLOGY. [XX. 



bile-pigment absorbed from the intestinal canal and excreted by 

 the urine. 



(2.) [Febrile Urobilin. This gives the dark colour to urines in fever. It 

 seems to be a less oxidised form of urobilin, is isolated in the same way, its 

 spectrum shows the band near F, and two additional bands, one near D and 

 one between D and E.] 



(3.) Indigo-forming Substance (Indican). This is derived from indol, 

 C 8 H 7 N, which is developed in the intestinal canal from the pancreatic diges- 

 tion ofproteids, and also from the putrefaction of albuminous bodies. It may 

 also be formed from bilirubin. In urine it is a yellow pigment, and is more 

 plentiful in the urine of the dog and horse. It exists in the urine as a 

 conjugated sulpho-acid salt of potassium, viz., as indoxyl-sulphate of potas- 

 sium (C 8 H 6 NS0 4 K). 



13. General Eeactions for Urine Pigments. 



('I.) Add to normal urine a quarter of its volume of HC1, and 

 boil = a fine pink or yellow colour. 



(b.) Add nitric acid = a yellowish-red colour, usually deeper than 

 the original colour. 



(c.) To two volumes of sulphuric acid in a test-tube add one of 

 urine, but drop the latter from a height. The mixture becomes 

 more or less garnet-red if indican be present. 



(d.) Add acetate of lead = a precipitate of chloride, sulphate, and 

 phosphate of lead. Filter ; the filtrate is an almost colourless 

 solution. This substance is used to decolorise urine for the sac- 

 charimeter. 



(<?.) Filter urine through animal charcoal; the urine will be 

 decolorised. 



(/.) If possible, obtain a dark-yellow coloured urine, and perform the 

 following test :- Take 40 drops of urine -f- 3 to 4 cc. of strong HC1 and 2 to 3 

 drops of HN0 3 ; on heating, a violet red colour with the formation of true 

 rhombic crystals of indigo-blue indicates the presence of indican. 



(g.) Test for Indican. Mix equal volumes of urine and HC1, add, drop by 

 drop, a saturated solution of chloride of lime (i.e., bleaching powder, which 

 also contains hypochlorite of calcium) = a blue colour. Shake up with chloro- 

 form and the blue colour is absorbed by the latter. 



14. Phenol (carbolic acid), 0^11,0, occurs in the urine as phenol-sulphate of 

 potassium, C 6 H - S0 3 OK. There is a corresponding salt of Cresol, most 

 abundant in the urine of herbivora. Add sulphuric acid to urine until the 

 latter contains 5 per cent, of the acid. Distil as long as the distillate becomes 

 cloudy with bromine water. Test the distillate as follows : 



(a.} Bromine water = precipitate of tri-bromo-phenol (CgH^BryOH). 



(6.) Neutralise and add neutral ferric chloride = violet colour. 



(c.) Heated with Millon's reagent it gives a red colour. (See also p. 82.) 



The patholog'cal pigments bile, blood, &c. occurring in urine 

 will be referred to later. 



