THE CONSTITUENTS OF THE BILE. 317 



the salts of the biliary acids in alcoholic extract are precipitated and thus isolated. 

 It depends on the production, from the reaction between sugar and sulphuric 

 acid, of furfurol, which is stained red in the presence of the biliary acids. Instead 

 of sugar a o.i per cent, aqueous solution of furfurol may be employed with advan- 

 tage for this reaction. 



The biliary acids are formed in the liver, as extirpation of this organ 

 is not followed by their accumulation in the blood. 



The manner in detail in which the production of the nitrogenous biliary acids 

 takes place, is unknown, although they are supposed to result from albumin. A 

 generous proteid diet increases the secretion of bile. Taurin contains the sulphur 

 of the proteid; the biliary acids contain from 4 to 6 per cent, of sulphur. Probably 

 the substance of the red blood-corpuscles broken up in the liver takes part in 

 their production. 



The Biliary Pigments. Fresh human bile and that of some animals 

 is yellowish brown in color, due to the bilirubin present which is 

 combined with an alkali. Under the influence of oxygen, heat and 

 light, bilirubin is transformed by oxidation into a green pigment, biliver- 

 din. This predominates in the bile of herbivora and of cold-blooded 

 animals, and likewise often in the state of hunger. 



(a) Bilirubin, C 32 H 36 N 4 O 6 , from 0.15 to 0.25 percent, in human bile, 

 according to Stadeler and Maly in combination with an alkali, crys- 

 tallizes in transparent, sorrel, clinorhombic prisms. It is insoluble in 

 water, but soluble in chloroform, by means of which it can be separated 

 from biliverdin, which is insoluble in chloroform. It combines with 

 alkalies as a monobasic acid and is thus soluble. It is identical with 

 hematoidin. 



It is most easily prepared from red gall-stones formed of bilirubin and lime, 

 which are triturated, the lime being dissolved out by means of hydrochloric acid. 

 On agitation with chloroform the bilirubin is taken up. The derivation of bilirubin 

 from hemoglobin is not to be doubted, on account of its identity with hematoidin. 

 Probably red blood-corptiscles are broken up in the liver, and their hemoglobin is 

 converted into bilirubin. 



In normal bile from a dog, a pigment is not rarely present having the spectral 

 properties of methemoglobin, and which perhaps represents a body intermediate be- 

 tween the hemoglobin and the coloring-matter of the bile. 



' (b) Biliverdin, C 3 2H 36 N 4 O 8 , is an oxidation-stage of bilirubin, from 

 which it can be obtained by various oxidizing processes. It is readily 

 soluble in alcohol, with great difficulty in ether, and not at all in chlo- 

 roform. It is present in large amount in the placenta of the dog. 

 It has not as yet been possible to reconvert it into bilirubin by means 

 of reducing agents. 



Gmelin's Test. Bilirubin and biliverdin, which, in addition to the bile, are 

 occasionally found also in other fluids, at times in the urine, are demonstrated by 

 Gmelin's test. If to the fluid containing the substances named are added several 

 cubic centimeters of nitric acid and one drop of nitrous acid, which are permitted 

 to flow carefully from the edge down the sides of a conical glass, without agitation, 

 a play of colors results as follows: green (biliverdin), blue, violet, red and yellow. 



(c) If the addition of acid is stopped when the- color becomes 1>lue. thus pre- 

 venting further oxidation, a stable transformation-product remains, name' 

 cyanin. This has a blue color in acid solution, a violet color in alkaline solution, 

 and it exhibits two ill-defined absorption-bands at D. Haycraft and Schofield 

 were able to change this back by reduction with ammonium sulphid. 



Fluids containing biliary pigment, if boiled for from three to five minutes with 

 one-third formalin, acquire an emerald-green color, which is changed to amethyst 

 violet on addition of hydrochloric acid. 



(d) Small amounts of bilijuscin (bilirubin + water) have also been found in 

 gall-stones and putrid bile. 



