ON bromination, the isomeric forms of 1-carboxy-4-methylcyclohexane-1-acetic acid (m.p. 173° and 137°)1 furnished monobromo acids, which gave the corresponding hydroxy acids on being heated with aqueous sodium carbonate. Oxidation of the hydroxy acids with alkaline permanganate gave rise, however, to isomeric forms of 4-methylcyclohexane-1: 1-dicarboxylic acid, which depressed each other's melting points. Similar observations were made in the 3-methylcyclohexane series.