The histochemical recognition of certain guanidine derivatives.

AKAGUCHI'S test for arginine depends on the production of a pink or red colour when certain guanidine derivatives are treated with a-naphthol and sodium hypochlorite in alkaline solution (Sakaguchi, 1925). This test had been familiar to biochemists for 19 years before it was independently adapted to histochemical use in the same year by Serra (1944) and myself (1944). Our results were published on opposite sides of the battle-front. The purpose of the present paper is to discuss the validity of Sakaguchi's test and to present my histochemical adaptation of it in its latest form.