“The facility which Sims’ original speculum gives for exploration is very great…but, unfortunately it cannot be employed without a skilled assistant for it to be of real value since when elevating the posterior vaginal wall the anterior must be depressed by an instrument held in the other hand.  Thus, both hands are occupied, and the operator is bereft of the power to proceed.  The object of my alteration is to liberate one hand in order that one may proceed with further steps of examination.  Accordingly, the usual blade, a, is placed within the vagina and the inferior blade, b, placed on the outer surface of the sacrum while the anterior wall is elevated by the depressor, c, and thus one hand is free.”   Thomas - 1872