It is our purpose in this series of papers to present the results of experiments designed to reinvestigate certain aspects of the related subjects of intracranial hydrodynamics and cerebral edema. The work was prompted by the disagreement that seems to exist in the past and current literature with regard to such important questions as the relative dangers of ventricular and lumbar punctures, the etiology of untoward effects following rachicentesis, the causes of "herniation" of the brain stem and other topics that are necessarily related to our subject. The present paper deals with the method evolved for investigating intracranial hydrodynamics in fresh human cadavers. The second communication will describe a series of animal experiments on the possible hydrodynamic etiology of edema of the brain. The third article will present a résumé of the extensive literature, report certain original experimental and clinical data and attempt a correlation of our findings with those