Administrative Medicine

well-illustrated presentation of electron microscopy of the mammalian choroid plexus by Wislocki and Ladman discloses many fine details of intracellular structure, some of which suggest strongly the presence of an active secretory process. The tissue culture experiments of Lumsden show that under the experimental conditions the choroid villus is capable of absorbing and concentrating dye solutions and maintaining a pH gradient. Other anatomical studies deal with structural details of choroid plexus innervation, arachnoid villi, nerve root sheaths, and the perivascular and supposed tissue spaces of the brain. Of greatest interest to this reader were the various papers and discussions relating to radioactive isotope studies of the cerebrospinal fluid. The statements of Selverstone are of great value in dispelling the confusion which has arisen from false interpretation of observations made in earlier isotope work -unwarranted conclusions which seemed to invalidate the classical concepts of Weed. Bowsher has demonstrated a higher sodium concentration in CSF collected directly from the choroid plexus than in free ventricular or cisternal fluid, and suggests that osmotic dilution of this initially hypertonic fluid is the mechanism of CSF formation. Unfortunately the number of observations is small, but further work may put this theory on a firmer basis. Dott and Gillingham suggest that localized expanding arachnoid pouches in communication with the general subarachnoid space may be formed by the pumping action of pulsating cerebral arteries in the region, a concept which is not quite convincing. Other papers of a clinical or pathological nature do little more than re-explore familiar ground. This symposium succeeds in presenting diverse current ideas about the riddle of the cerebrospinal fluid, raises many interesting questions, answers few. SAUL A. FRANKEL