484 PATHOLOGICAL PIGMEXTATION 



the disease. Spmnt suggests that the diabetes may be referable to 

 diminished oxidative power because of disturbances in the iron-con- 

 taining constituents of the tissues, assuming these iron compounds to 

 be catalytic agents in oxidizing processes. 



ICTERUS ■« 



Pigmentation of the tissues of the hody in jaundice depends upon 

 the presence in them of bile-pigments, which usually have been formed 

 in the liver and reabsorbed either into the lymph or blood (or both). 

 However, a pigment that seems to be chemically identical with bili- 

 rubin {hematoidin) may be formed from hemoglobin liberated on the 

 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. — Biliruhin is of a reddish-yellow color, and it is the chief pig- 

 ment of human hile. Its formula is Cg^H^sNiOu or C.,3H3oN40,;, and its relation to 

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

 presses the manner in which blood pigment may Ijc 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: 



Ca^H^^N.O.Fe + 2HoO = C^JI.s'^fi, f 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, Init is more soluble 

 in alcohol and in chloroform. 



Biliverdin, C;,4H38N40s, as its formula indicates, is an oxidation product of 

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

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

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

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

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



The various other biliary pigments, namely, hilifuscin, hiliprdsin. rliolrprnniii.'^ 

 hilihininn, and hilicyanin, are probably not normal C(mstituents of bile, but are 

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

 pigment similar to urobilin may be present in normal bilo. The total amount of 

 pigment's present in liile is probably not far from one gram per liter; ratlier under 

 than above this amount. 



Etiology of Icterus. — Although hematoidin, wliich is isomeric if 

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

 red corijuscles are broken u]) in hemoiThagic extravasations, and 



. 76 Literature by Stadelmann, "Der Icterus," Sluttgart, 1S91; Minkowski, 

 Ergebnisse der Pathol., 1895 (2), 079. 



77 See Ouillain and Troisier, Semaine MM., 1909 (29). l;?:5: Widul and .Jolt rain, 

 Arch. mr-d. expC'r., 1909 (21). (541. 



78l)iinzelt, Cent. f. Patli., 1909 (20). 900. 



70 See Kiister, Zeit. physiol. Chem., 1906 (47), 294. 



