Abstract
We found that a 15-min treatment of tissue sections with 2 M/l H2O2 dissolved in 6 M/l sulphuric acid strongly suppresses the argyrophilia of tissue elements, thus lacilitating selective silver intensification in histochemical procedures. When applied inserted between the 3,3′-diaminobenzidine reaction and physical development, this treatment allows the selective and sensitive visualization of very low levels of peroxidase activity.