It has been urged by Gesell ( '25) that carbon dioxide exerts a depressing action upon the rate of oxygen consumption of brain tissue. Recent experiments of Necheles and Gerard ('30) suggest that carbon dioxide suppresses oxidations in peripheral nerve. The experiments to be reported here were designed to test directly the influence of carbon dioxide upon the respiration of nerve. They have been carried out upon the lateral-line nerve of the smooth (Mustelus canis Mitchell) and the spiny (Squalus acanthias) dogfish during the summers of 1930 and 1931. This nerve is composed of very uniform, medullated, sensory fibers (Parker, '25). It can be easily and quickly dissected from the side of the fish and yields a clean smooth trunk, thick anteriorly and diminishing posteriorly.
EXPERIMENTAL METHOD
The fish was killed by a blow and the lateral-line nerves dissected out with great care to avoid stretching. Any adhering muscle tissue was removed. The nerves were then placed upon the stimulating electrodes of the tonometers. These tonometers (fig. 1) consisted of a glass tube about 2 em. in Aided by a grant from the Helidricks Research Fund, Syracuse University.