ICTERUS 489 



breaking up of red corpuscles, and possibly this may be produced in 

 sufficient amounts outside of the liver to give rise to general icterus. 

 Certainly the local greenish-yellow pigmentation occurring in the 

 vicinity of extravasations of blood, due to hematoidin formation, may 

 be looked upon as a "local jaundice," and in icterus hematoidin^^ 

 crystals may be found in the tissues.-^ 



Bile-pigments. — Bilirubin is of a reddish-yellow color, and it Is the chief pig- 

 ment of human bile. Its formula is CsiHssN-iOe or CssHjeN^Oe, and its relation to 

 hematin, from which it is formed, is shown by the following formula, which ex- 

 presses the manner in which blood pigment may be converted into bilirubin by 

 the liver under normal conditions, and into hematoidin (its isomer) in the tissues 

 and fluids of the body in pathological conditions: 



CaiHa^N.OjFe + 2H2O = C3.H38N4O6 + FeO. 

 (hematin) (hematoidin or 



bilirubin) 



Bilirubin is not soluble in water, but dissolves in the alkaline body fluids as a 

 soluble compound, "bilirubin alkali." It is very slightly soluble in ether, ben- 

 zene, carbon disulphide, amyl-alcohol, fatty oils, and glycerol, but is more soluble 

 in alcohol and in chloroform. 



Biliverdin, 0^411:1^^40$, as its formula indicates, is an oxidation product of 

 bilirubin. Bilirubin in alkaline solutions will oxidize into biliverdin merely on 

 exposure to the air, and the change from yellow to green of icteric specimens when 

 placed in oxidizing solutions (e. g., dichromate hardening fluids) is due to the 

 formation of the green biliverdin. Biliverdin is the chief pigment of the bile of 

 carnivora, but it is also present in varying amounts in human bile. 



The various other biliary pigments, namely, bilifuscin, biliprasin, choleprasin,-* 

 bilihumin, and bilicyanin, are probably not normal constituents of bUe, but are 

 oxidation products of bilirubin, and are found chiefly in gall-stones (q. v.). A 

 pigment similar to urobilin maj'- be present in normal bile. The total amount of 

 pigments present in bile is probably not far from one gram per liter; rather under 

 than above this amount. 



Etiology of Icterus. — ^Although hematoidin, which is isomeric if 

 not identical with bilirubin, may be formed outside of the liver when 

 red corpuscles are broken up in hemorrhagic extravasations, and 

 possibly also when they are broken up within the vessels by hemolytic 

 agents, yet it was formerly held that a true general icterus does not 

 occur without the liver being implicated. This view rested on evi- 

 dence of various sorts. First, the classical experiments of Minkowski 

 and Naunyn,-^ which demonstrated that in geese the production of 

 hemolysis by means of arseniuretted hydrogen leads to icterus, but if 

 the livers of the geese have been previously removed, no icterus follows 

 the poisoning. Second, the repeated demonstration that in icterus 

 produced by septic conditions, poisoning, etc., which was formerly 

 looked upon as Si "hematogenous" icterus, the urine contains bile 

 salts as well as pigment, indicating an absorption of bile from the liver. 

 Third, the finding of histological evidence that in so-called hematogen- 



" See Guillain and Troisier, Semaine Med., 1909 (29), 133; Widal and Joltrain, 

 Arch. med. expcr., 1909 (21), 641. 



•" Dunzelt, Cent. f. Path., 1909 (20), 966. 



24 SeeKiister, Zeit. physiol. Chem., 1906 (47), 294. 



" Arch. f. exp. Pathol, u. Pharm., 18S6 (21), 1. 



