[Reaction of the pre-edematous brain to an increase in venous pressure]

Changes in the volume of the open brain were recorded in rabbit experiments ("chest-head" preparation) in a series of tests with controlled increase in general venous pressure by approximately 13 mm Hg. At the beginning of the experiments the changei in the volume of the open brain and general venous pressure occurred parallely to each other, but later, when the brain became preedematous, hysteresis was detected on the curves of their dependence. Hysteresis increased gradually during the experiment, indicating that impedement of blood drainage from the venous system of the brain and/or resorption of fluid from its tissue had begun to the development of stable edema. It is assumed that the predematous condition of the brain is caused by changes either in the mechanical properties of its tissue or in its osmolarity.