a dark brown, granular pigment that rotates the plane of polarized light and has other properties similar to formalin pigment; occurs in parasitic infection, such as those caused by Plasmodium malariae, around brain capillaries, and in fixed macrophages of spleen, liver, bone marrow, and lymph nodes; composed of excess protein, an iron porphyrin, and hematin left over from the metabolism of hemoglobin by the malarial parasite within the red blood cell.malarial pigment stain