THE EFFECT OF DISLOCATION OF CEREBROSPINAL FLUID UPON ITS PRESSURE

Abstract

Pressures of the cerebrospinal fluid were measured by bubble manometer and by open-end manometers of various bores in dogs of similar weight and size. Pressures recorded in manometers of 1 mm. bore did not vary greatly from those obtained with the bubble manometer. With larger open-end manometers, the pressure-alteration in the cerebrospinal fluid on tilting from the horizontal to the vertical positions, decreased in proportion to the amt. of fluid dislocated in the manometer. In animals of the same size there was a constant relationship between volume of fluid dislocated and pressure-change. By means of this relationship, expressed in the fraction dV/dP [where dV represents the difference in volume between the experiment with no displacement (bubble manometer) and the actual cc. change in any of the open-end manometers, while dP represents the difference in cm. of the pressure-change on tilting, between that recorded by the bubble manometer and those by any of the open-end manometers], accurate determinations were made of the volume-diminution in brain and cerebrospinal fluid, effected by intravenous hypertonic solutions. The value of the fraction dV/dP is a function of the volume of the system and of its physiological elasticity. The pressure-changes, on tilting from horizontal to vertical positions, were duplicated by an artificial system of glass tubes and tambours covered with rubber membranes. From this system a similar constant, expressing the relationship between fluid-dislocation and pressure-change was obtained, the magnitude of the fraction depending on the elasticity and capacity of the membranes.