The electrical response of the auditory mechanism in cold-blooded vertebrates

Abstract

In mammals the changes of electrical potential in the ear and 8th nerve are mainly due to the sound-receiving mechanism. The nerve must also register the action of the gravity receptors and semicircular canals, but the potentials due to these are swamped by the much larger cochlear effect. In cold-blooded vertebrates, on the other hand, impulses from the vestibular organs are often more prominent than those due to sound and have attracted more attention. Thus Ross (1936) has analysed the receptors in the frog’s labyrinth by recording from single fibres of the 8th nerve, and Löwenstein and Sand have studied the discharge from the semicircular canals in fish, but there has been little recent work on the electrical response to sound either in fish, amphibia or reptiles, though an early paper of Wever and Bray (1931) deals with the response in the terrapin. The present observations have been made on the alligator, the tortoise, the frog and the eel. These were chosen to offer a wide range of structure both in the middle and inner ear. A limited survey of this kind is not of much value from the point of view of comparative physiology, for there are many other species which must be investigated if we are to follow the development of the sound-receiving apparatus in the vertebrate. None the less, the results seem to be worth putting on record since they have some bearing on the general problem of the cochlear potentials and of the mechanism of the sensory endings.