Possible Chemical Nature of Tobacco Mosaic Virus

Abstract

DR. J. CALDWELL¹ has criticised some of our statements on the possible chemical nature of the virus of tobacco mosaic. We must point out that the essential precipitant used in the Vinson and Petrie method is not basic lead acetate but neutral lead acetate. We are also quite aware of the fact that the addition of two volumes of acetone to one of aqueous M/1 KH²PO⁴ solution produces a heavy precipitate of white rhombic crystals, but as Vinson and Petrie and ourselves were concerned with an M/15 solution of this salt, Caldwell's criticism is irrelevant. If acetone (two volumes) be added to an aqueous M/15 solution of KH²PO⁴ or to an eleuate prepared from healthy sap, only a faint white opalescence makes its appearance and a slight precipitate settles after many hours.