The Use of Pyrogallol to Demonstrate Peroxidase in Mammalian Blood Eosinophils

Canine blood films were fixed in a mixture of formaline (40% HCHO) and 95% ethyl alcohol, 1:9, for 30 sec, washed in distilled water and air dried. A mixture of 10% aqueous pyrogallol 6 ml and H2O2 (6% or 20 vols.) 0.1 ml were applied to the film, allowed to react for 6 min and then washed off with distilled water. The film was counterstained with May-Grünwald Giemsa, Leishman, or Giemsa stain. This method stains canine eosinophils specifically for the presence of peroxidase, but has variable effects on eosinophils of other mammalian species, depending on the type of fixative used. Modified techniques are described for 4 other mammalian species and the possible causes of the staining variations are discussed.