Duhamel and Rebiere(6)(7) showed that an injection of a trace of red colloidal selenium into rabbits increased urea excretion regularly. In other cases satisfactory results were claimed and the liver showed some lesions. The histological modifications produced by injections into rabbits are most apparent in the liver and kidneys. In the distribution of colloidal preparations in the animal body by injection, Duhamel and Juillard(8) found that the liver contained the greatest amount. Six years later the former(9) used a similar preparation introduced into the animal intravenously, and selenium was again found in the liver, although in smaller quantity. Sulphur compounds have similar physiological action. It is known that triphenylstibine sulphide, or sulphoform, (C₆H₅)₃SbS, has a curative effect in skin diseases, as it liberates “nascent” sulphur on the skin. It is equally natural to expect some organic selenium compound which liberates finely divided selenium to exert a remedial influence on animal bodies. The selenoquinazolone prepared in the course of this research and described more fully in another section of the paper, has this prospect. The quinazolone has the following structure: N /\ / \\ | | C-CH₃ | | | | | NH \/ \ / C Se Experiments were carried on at L’Institut Pasteur in Paris under the supervision of M. Borel for the treatment of cancer in mice. No human subjects were experimented upon, although results were claimed by using selenides and their oxidized salts. Selenium dyes were found to be medicinals, although no relation has yet been established between constitution of these organic dyes and their therapeutic value. Wassermann(10) made several eosin preparations, by coupling the sodium derivative with potassium selenocyanide. The red dyestuff thus prepared is stated to be easily soluble in water. Wassermann, Keysser and Wassermann(11) made experiments with it, chemotherapeutically, on animal tumors. When the solution was injected into mice tumors the latter turned red, accompanied by the softening of the tumor after the third injection and complete resorption after ten injections, unless the dose used was too great for the animal. In that case death often occurred. Good results were also reported, in connection with this experiment, on four different strains of mouse carcinoma and one strain of mouse sarcoma. In the latter case, relief was found sooner but the former disappeared more slowly. Another preparation was made later(12) and introduced into mice intravenously and again found to have good results. The following is the structure of 2-selenocyanideanthraquinone-- O C SeCN /\ / \ /\ / | | | | | | | | \/ \ / \/ C O which has also been reported to have medicinal uses(13). P. Ehrlich and Hugo Bauer(14) synthesized from p.p′-diamino-diphenyl- methane the red dye 3,6-diaminoselenopyronine.