BLOOD PIGMENTS 401 



specimens kept for microscopic purposes, irregular orange-yel- 

 low crystalline masses of hemoglobin may be found. This occurs 

 particularly if the blood has been acted upon by hemolytic 

 agents or has undergone putrefactive changes, and then is 

 hardened in alcohol. The crystals are either oxyhemoglobin, 

 or more often an isomeric or polymeric modification, parahemo- 

 globin (Nencki). Hemoglobin also enters cells unchanged, 

 imparting a diffuse yellowish color. 



In the decomposition of hemoglobin the first step is the 

 splitting of the globin (which does not form pigments) from the 

 hematin, from which many pigments may be derived. 



Hematin. The formula given for this substance by Nencki, 

 C 32 H 32 N 4 FeO 4 , has been generally accepted, although it is not 

 certain that the hematin of all animals is the same. It is found 

 frequently as an amorphous, dark-brown or bluish-black sub- 

 stance, in large, old extravasations of blood, but seldom in 

 small hemorrhages. As a pathological pigment, however, 

 hematin is by no means so frequently found as its derivatives. 

 Wherever formed its duration is transient, for it gradually splits 

 up into an iron-free pigment (hematoidin) and an iron-containing 

 pigment (hemosiderin). This change may be represented by the 

 following equation, according to Nencki and Sieber l : 



C 32 H 32 N 4 4 Fe + 2H 2 = 2C 16 H 18 N 2 O 3 + Fe. 

 (hematin) (hematoidin) 



Hematoidin may be found in old, large extravasations, as 

 orange-colored or red rhombic plates, first described by Yirchow. 

 Sometimes, however, hematoidin occurs in the form of yellowish 

 granular masses. It seems to be nearly or quite identical with 

 the bile-pigment, bilirubin, and it is probably the source of this 

 substance under normal conditions. When formed in excessive 

 amounts, either through increased destruction of corpuscles in 

 the vessels or in extravasations, the amount of bile-pigment is 

 increased (see " Icterus "). Possibly some of the hematoidin 

 becomes transformed directly into urobilin, and is then eliminated 

 in the urine. 



Hemosiderin 2 is relatively insoluble, and, therefore, is 

 more slowly removed when formed in hemorrhages, and more 

 abundantly deposited in the tissues when formed after excessive 

 hemolysis. According to Neumann, hemosiderin is produced 

 only under the influence of living cells and in the presence of 



1 Arch. exp. Path. u. Pharm., 1888 (24), 440. 



2 See Neumann, Virchow's Arch., 1888 (111), 25; 1900 (161), 422; 1904 

 (177) 401 ; also Arnold, ibid., 1900 (161), 284. 



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