. . . . . . . . . . . . . . "STUDIES ON LACTONES RELATED TO THE CARDIAC AGLYCONES. III. THE PROPERTIES OF \u03B2-SUBSTITUTED \u0394\u03B1,\u03B2-BUTENOLIDES AND A SUGGESTED REVISION OF THE STRUCTURE OF THE SIDE CHAIN OF THE DIGITALIS-STROPHANTHUS AGLYCONES" . .