In 1922 I published with Sekiya a new peroxidase reaction (often quoted in the literature as Sato and Sekiya's peroxidase stain or as Sato's peroxidase reaction). As my proper object of research was infantile nutrition, I made light of our own peroxidase reaction-which was then used only for the differentiation of myeloic and lymphatic leucocytes in leukemic cases (then very rare). But in course of time it gave me a hint to finding 1) the localisation of a brain lesion, 2) the poison of infantile beriberi (methyl glyoxal 1934; strictly chemical identification 1950) and 3) a new disease (Chédiak-Higashi's Disease).