Darkfield illumination improves microscopic detection of metals in Timm's stained tissue.

Deposits of trace or toxic metals can be quickly identified by light microscopical surveys of tissue sections stained for metals by variants of Timm's silver enhancement method. The present work shows that the small, isolated silver grains that label isolated deposits of metal in tissue are undetectable in brightfield light microscopy but are easily detected in darkfield microscopy. Darkfield illumination is therefore recommended for improving the detection of trace or toxic metals in tissue.