Okamoto found that not only alloxan but also dithizone or oxin can produce diabetes in the test animals and proposed a zinc theory of diabetes. As dithizone and oxin react not only with zinc but also with many other metals, such as copper, nickel, cobalt, bismuth, silver etc, the author investigated the copper and zinc content of blood after intravenous administration of dithizone (100 mg per kg of bodyweight) or oxin (50 mg per kg of bodyweight) to rabbit by chromatographic method devised by the author. Both zinc and copper in blood decreased soon after the injection of the above-mentioned reagents and recovered only slowly after 24 - 48 hours.