The Threshold Sensitivity of the Tympanic Muscle Reflexes

Abstract

That the muscles of the middle ear are normally made to contract through a reflex action of sound was first clearly indicated by the work of Hensen¹ in 1878. His experiments were carried out on dogs and were concerned only with the tensor tympani muscle, which was seen to contract when a loud sound was applied to the ear. Similar observations were made by Kato² in 1913 on the stapedius muscle, with cats and rabbits as the experimental animals. Since then there have been many further experiments on these and other animals, including man, in which the reflex responses of these muscles have been demonstrated. So far, however, little has been reported on the intensities of the sounds required to elicit the reflexes. The most extensive quantitative results were obtained by Lorente de Nó and Harris³ on the rabbit by visual observations of the muscle action. They