A review of theories of narcosis has been made, and some correlations between constitution and activity have been presented for the aliphatic hypnotics;The close and important relationship of dibenzofuran and its derivatives to morphine has been discussed. The following derivatives to morphine has been discussed. The following derivatives to morphine has been discussed. The following derivatives of dibenzofuran haven been prepared for use in physiological tests: 2-, 3-, and 4-amino-, 2- and 3-hydroxy-dibenzofuran, and 2- and 3-dibenzofurancarboxylic acids;A necessary study of nuclear substitution in dibenzofuran has been made prior to the preparation of derivatives for physiological tests. It has been shown that homonuclear substitution results when 2-discetaminodibenzofuran is brominated or nitrated. Heteronuclear substitution occurs when 3-nitrodibenzofuran is brominated. Both heteronuclear and homonuclear substitution take place when 2-bomodibenzofuran is nitrated;The hydroxydibenzofuran formed by passing resorcinol over heated tungstic oxide has been shown to be 3-hydroxydibenzofuran; and, a low melting isomer formed during nitration of dibenzofuran has been found to consist, in part, of 2-nitrodibenzofuran. The significance of these two facts is discussed with reference to the space formula of dibenzofuran and purported anomalous substitutions.