EXPERIMENTAL STUDIES ON THE INFLUENCE OF HYPER-AND HYPO-TONIC SOLUTION UPON THE FUNCTION AND THE MORPHOLOGY OF THE INNER EAR

Abstract

Up until the present time, many theories on the relation between the cerebro-spinal pressure or labyrinthine pressure and the cochlear function have been proposed. These proposals have been based on experiments conducted by spreading of pressure through the cochlear aqueduct. However, the author emphercises that more attention should be given to the condition and nature of the cochlear blood vessels. The author bases his conclusion on the following experiments: I. In order to follow up the influence upon the cochlear function at the time of variations in pressure of the cerebro-spinal fluid due to intravenous injection of hyper- and hypo-tonic solution, the author first measured the variation of the cochlear response of two groups of cats, normal and cats with obstructed cochlear aqueduct. By hypertonic solution fall of both cochlear response and cerebro-spinal pressure was observed. By hypotonic solution a fall in the cochlear response was not observed but a rise in cerebro-spinal pressure was noted. The results were the same in both groups, the normal and controlled cats. Thus, Hughson Crowe's opinion that variations of intralabyrinthine pressure through the cochlear aqueduct should be denied. II. After intravenous injection of hyper- and hypo-tonic solution, the histology of the inner ear was observed. Two contrary views of the blood vessels were observed. 1. Enlargement of blood vessel cavities of stria vasculi caused by the hypertonic solution. 2. Contraction of blood vessel cavities of stria vasculi by hypotonic solution. III. To supplement the above experiments, the author measured the blood pressure of the arteries of the human retina before and after injections of hyper- and hypo-tonic solution. In comparison to cats, only small amounts of hyper- and hypo-tonic solution were injected. However, sharp and contrary variations of blood pressure were observed; i. e. rise of blood pressure of the retina due to the hypertonic solution and fall due to the hypotonic solution.