134 Microscopic Histochemistry 



the benzidine reaction can be catalyzed also by nonprotein 

 heme compounds. 



b) Hemosiderin is a yellowish, brownish, or greenish- 

 brown granular pigment which resists the bleaching action 

 of hydrogen peroxide and of permanganate and is not argen- 

 taffin. It does not dissolve in dilute acids, or alkahs. It can be 

 identified by the Prussian blue test (p. 38). 



c) Malaria pigment is an amorphous brown-black granu- 

 lar substance, soluble in dilute alcoholic alkalis or Barrett's 

 solution (p. 132); it is bleached by 3 per cent hydrogen per- 

 oxide within 2 hours. It has repeatedly been identified as 

 hematin."^ Naturally, the pigment will not give a direct reac- 

 tion for iron. After destroying the organic matter with chlo- 

 rine, hydrogen peroxide, or alkali, a positive Prussian blue 

 reaction can be obtained.^ It is not possible to differentiate 

 malaria pigment from formalin pigment histochemically. In 

 diagnostic cases, the formation of formalin pigment must be 

 prevented by proper fixation. 



B) Iron-free pigments —Bile pigments appear under the 

 microscope as yellowish-green, more or less coarse granules 

 which are not bleached by hydrogen peroxide or by perman- 

 ganate and are not argentaffin. They are slowly converted by 

 oxidants (hydrogen peroxide, Lugol's solution,^ nitrous 

 acid,^^ dichromates, etc. ) into green biliverdin. Hematoidin 

 is chemically identical with bilirubin and shares its reactions. 



2 ) Phenolic pigments.— 



A) Melanin is an oxidation-polymerization product of 

 dioxyphenylalanine and possibly also of tyrosine.^^ It forms 

 yellowish-brown or grayish to almost jet-black granules, in- 



7. Sinton, J. A., and Ghosh, B. N.: Rec. Malaria Survey India, 4:205, 

 1934; Morrison, D. B., and Anderson, W. A. D.: Pub. Health Rep., 57:90, 

 1942; Devine, J., and Fulton, J. D.: Ann. Trop. Med., 36:167, 1942. 



8. Kosa, M.: Virchows Arch. f. path. Anat., 258:186, 1925; Okamoto, K.: 

 Taishitzu Gaku Zasshi, 13:55, 1944. 



9. Stein, J.: Compt. rend. Soc. de biol., 120:1137, 1925. 



10. Okamoto, K., Sengoku, M., and Hirotani, N.: Taishitzu Gaku Zasshi, 

 14:30, 1948. 



11. Hasebroek, K.: Fermentforsch., 5:1, 1922; Sato, K., and Brecher, L.: 

 Arch. f. mikr. Anat., 104:649, 1925. 



