Chapter \^ 



Pigments and 

 Minerals 



Pigments are a heterogeneous group of substances containing enough 

 natural color to be visible without staining. Sometimes, however, color is 

 added to give them more intense differential staining. Some pigments 

 are artifacts, such as formalin pigment (page 7). Others, exogenous 

 pigments, are foreign pigments that have been taken into the tissue in 

 some manner. Carbon is a common pigment found in the lungs of city 

 dwellers, particularly of people from coal-burning cities. Endogenous 

 pigments are found within the organism and arise from nonpigmented 

 materials. Iron-containing hemoglobin can become broken down into 

 iron-containing pigment, hemosiderin, and a noniron-containing pig- 

 ment, hematoidin, or bilirubin (brown) which can be oxidized to 

 biliverdin (green). Normal hemoglobin, when not broken down into 

 hemosiderin, will not show a positive Prussian blue reaction (page 233). 

 The iron is masked or occult, and the organic part of the hemoglobin 

 molecule must be destroyed, the iron must be unmasked. Hydrogen 

 peroxide has become the reliable reagent for this purpose, producing 

 ferric oxide, and finally a fairly good Prussian blue reaction. 



Melanin (brown or black pigment) is foinid normally in the skin, 

 hair, and eye, but may occur pathologically anywhere in the body, 

 Lipofuscin, sometimes kno\vn as the "wear and tear pigment, can be 

 foinid in the heart muscle, adrenals, ganglion cells, and liver. Melanin 

 and lipoftiscin are brownish pigments stainable by fat dyes and some 



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