ON THE SOURCE OF THE CEREBROSPINAL FLUID. THE DISTRIBUTION OF BROMIDE AND IODIDE THROUGHOUT THE CENTRAL NERVOUS SYSTEM

¹ From the Department of Pharmacology, New York University College of Medicine

1. Bromide and iodide, injected intravenously, distribute evenly in the extracellular fluid throughout all parts of the central nervous system.

2. Injected into the cisterna magna they distribute unevenly, in greater amounts in parts adjacent to the cistern, in least amounts in parts most distant.

3. When the spinal cord and its membranes are isolated by ligation separating them from the cistern, bromide injected intravenously enters the spinal fluid below the ligature.

4. When iodide is injected intravenously it appears promptly in the extracellular brain fluid and the lateral ventricles and in equal concentrations. There is some lag in its reaching the same concentration in the cortical subarachnoid fluid, and a still longer lag in its reaching the same concentration in the cisternal fluid.

5. We conclude from our experiments that anions enter the cerebrospinal fluid as readily from the capillaries in the brain substance as from the ventricular choroidea. As we view it, they pass from the plasma into a pericapillary and perineuronal space constituting the extracellular tissue space. In this first passage they must cross a barrier which offers some selective hindrance to their course. From the extracellular spaces they enter the perivascular spaces and from there pass into the subarachnoid fluid.

6. As the passage of the anions may be identified with the origin of the cerebrospinal fluid, our experiments demonstrate the extra ventricular source of this fluid. Reasons are given for considering the ventricular source as of minor importance.

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