Studies on the Role of the Cerebrospinal Fluid in Brain Metabolism as Measured with Radioactive Phosphate¹

Summary. We injected P 32 into Cisterna magna of rabbits. The speed with which this P 32 enters into the brain has been determined. It was found that the radioactivity increases gradually in the different parts of brain with approximately the same rapidity. The maximum was reached after 35 minutes. The turnover of radioactive orthophosphate to organic bound phosphate in brain was measured. The different theories for the brain protective barriers have been discussed. The data supports the view that there are two ways of supplying the brain with P 32 . Some minor parts mainly the hypophysis, the pineal body, the plexus chorioidei and the vegetative centers in hypothalamus are supported mainly by the blood. The nervous tissue on the other hand seems to exchange phosphate via the cerebrospinal fluid.