402 PATHOLOGICAL PIGMENTATION 



oxygen, while hematoidin arises independent of cellular activity. 1 

 Milner 2 considers that, under similar conditions, an iron-con- 

 taining pigment is also formed, which differs from hemosiderin 

 in having the iron so combined that it cannot react with the 

 usual reagents ; this pigment may later change into hemosiderin. 

 Up to the present time we do not know the chemical nature of 

 hemosiderin, nor its exact fate in the body, but it is probably 

 utilized in the manufacture of new hemoglobin, for it is known 

 that the iron liberated when hematin is broken up in the body 

 under experimental conditions is deposited and not eliminated 

 (Morishima 3 ). 



Unstained hemosiderin generally appears in the form of brown 

 or yellowish-brown granules, and not as crystals. After a time 

 it is taken up and deposited to a large extent in the liver, spleen, 

 bone-marrow, and kidney, either as hemosiderin or possibly as 

 some other iron compound of similar nature. From these sites 

 it seems to be later taken up to be utilized in the manufacture 

 of new red corpuscles. 



Hematoporphyrin. This substance is readily formed 

 from hematin through removal of the iron, as shown by the 

 following reaction : 



C 32 H 32 N 4 Fe0 4 + 2H 2 O + 2HBr = 2C 16 H 18 N 2 O 3 + FeBr 2 + H 2 . 

 (hematin) (hematoporphyrin) 



The formation of hematoporphyrin from hematin also occurs 

 readily in the animal body, provided that the hematin is in a 

 reduced condition, according to Laidlaw, 4 but not when oxidized. 



The structural formula is believed to be as shown below : 



CH 2 CH 2 



HC-C C(OH) - (OH)Cf\ C-CH 



, 



\/ 



Physiologically, this pigment is of great interest, because of 

 the close chemical relation that it has been found to bear to 

 chlorophyll, 5 with which hemoglobin is so closely related func- 

 tionally. It is also interesting to consider that whereas carniv- 

 ora obtain much hemoglobin in their food, herbivora obtain 



1 The accumulation of iron in the liver which follows poisoning with 

 hemolytic agents, is not prevented or diminished by preliminary removal of 

 the spleen (Meinertz, Zeit. exp. Path. u. Ther., 1906 (2), 602). 



2 Virchow's Arch., 1903 (174), 475. 



3 Arch. exp. Path. u. Pharm., 1898 (41), 291. 



4 Jour, of Physiol., 1904 (31), 464. 



5 For literature see Abderhalden, " Lehrbuch der physiol. Chemie," 1906. 



