Liver pigment. A: Arrows point to pigment in both 14-day and 90-day liver tissues. The 14-day tissue has more Kupffer cells filled with pigment. The 90-day tissue has pigment but fewer Kupffer cells with pigment. B: Section of liver pigment stained with PAS, Perl’s iron, Schmorl’s, and acid fast. Schmorl's stain has some of the slightly blue reaction for lipofuscin, but the other lipofuscin stains (PAS, acid fast) do not have the characteristic color for lipofuscin. The Perl’s iron stain is negative for iron. Magnification: ×400.