The Cerebral Circulation

A. HYPERTONIC SOLUTIONS The purpose of this paper is to describe some of the vascular changes in the brain following the administration of strongly hypertonic solutions and to compare these changes with those following simple withdrawal of cerebrospinal fluid. In a previous paper of this series 1 it was reported that blood vessels in the pia constricted after intravenous or intraperitoneal injections of hypertonic solutions. This report was based on few experiments and was of a preliminary character. Recently, with improved technic the earlier work has been repeated and a much larger series of experiments performed. We believe now that the previous conclusions should be modified. Method. —Cats anesthetized with amytal (sodium barbiturate) or dial 1a (diallyl barbituric acid and ethyl carbamate) given by intraperitoneal injection were used in these experiments. Observation and measurement of pial vessels were carried out through a cranial window, 2 and photomicrographs were taken with