Middle ear sound transmission: a field of early interest to Merle Lawrence.

Merle Lawrence, together with his teacher, E.G. Wever, made early contributions to the problem of middle ear sound transmission. Experiments were mostly done in cats and studied the effects of stepwise destruction of the middle ear on cochlear input and the effects of changes in middle ear air pressure on sound transmission. Their experiments provided the first physiologic evidence that the origin of auditory distortion lies in the inner ear, not in the middle ear. Lawrence also demonstrated a dual innervation of the tensor tympani muscle. With the aid of newer instrumentation, the authors studied the effects of alterations of the middle ear cavity configuration, stepwise removal of the middle ear structures, restriction of ossicular mobility, and ossicular mass loading. Our experiments caused partial decoupling of the tympanic membrane and distortion of the axis ligaments, the apparent weak elements of the middle ear system in cats. The placement of the prosthesis along the mallear handle did not affect sound transmission, as long as the connection between malleus and prosthesis was made inflexible.