Effect of labyrinthine stimulation on the vagus control of the heart.

The work presented in this paper is the first of a series of studies which were undertaken with the view of determining the existence of a reflex path between the vestibular nerve and the autonomic or visceral nervous system. This investigation was prompted by a two-fold purpose: to establish, if possible, the existence of a tonic influence of the kineto-static labyrinth on the visceral nervous system, and to determine the physiological relationship between the two; and to establish the presence of a phenomenon which would be applicable to practical use from a clinical standpoint.

The labyrinth exerts a tonic influence on the general body musculature through its intercommunications with the somatic nervous system. The effects of the labyrinth on the visceral nervous system are not nearly as obvious nor as easily demonstrable as its effects on the somatic nervous system. For example, the stimulation of the vomiting center which occurs during the performance of the labyrinthine tests, or during an attack of seasickness, may be the result of cerebral impulses produced by the cumulative nausea, or as some authorities believe, may be produced by a direct reflex action of the hyperactivated labyrinth upon the center in the dorsal nucleus of the vagus.

That an interrelation exists between the visceral nervous system and the labyrinth is apparent when one considers that tinnitus is a common symptom accompanying disturbances of the viscera in other parts of the body. Woakesl considers that impulses from the stomach pass by way of the vagus nerve to the inferior cervical ganglion, where a communication is established with the nerves which regulate the amount of blood supply to the inner ear through the internal auditory artery The vascular changes thus produced, cause the tinnitus.