CEREBRAL CIRCULATION: XII. THE EFFECT ON PIAL VESSELS OF VARIATIONS IN THE OXYGEN AND CARBON DIOXIDE CONTENT OF THE BLOOD

Abstract

There is increasing evidence that chemical alterations of the blood, and especially changes of the acid-base equilibrium, have an important regulatory influence both on cerebral circulation and on respiratory movements. In this paper, we shall present observations which are intended to clarify these relationships. Numerous observers have reported that a dilatation of vessels of the brain occurs during asphyxia.1Observations by most of these authors have been by indirect methods, such as measurements of brain volume, of resistance to blood flow, or of the pressure in cerebral vessels. Florey2made use of direct observation but did not employ a window. In the experiments conducted in this laboratory, vessels of the pia were observed directly through a window in the skull, which procedure preserved the normal closed box arrangement. In confirmation of the observations of the previously mentioned authors, it has been our experience that a period of apnea