A Comparison of Ultrafilterable Serum Calcium and Cerebrospinal Fluid Calcium in Humans

Cameron and Moorhouse1 have proposed using the cerebrospinal fluid calcium as a measure of the diffusible calcium of the blood plasma, arguing that the choroid plexus as a living, colloid impermeable membrane gives us a more perfect distribution of the diffusible constituents of the blood than can be obtained in any in vitro manner. This implies both that the cerebrospinal fluid is formed by a process of diffusion rather than of active secretion and also that the fluid is continuously in diffusion equilibrium with the constituents of the plasma. Whether the cerebrospinal fluid is formed by an active process of secretion or is simply a dialysate of the blood plasma is still a mooted question.Histological data and evidence from the mechanics of circulation, favoring the dialysis theory have recently been reviewed by Fremont-Smith.2 It has been pointed out by Updegraff, Greenberg and Clark3 and by Fremont-Smith,2 that the published data of various authors for the amounts of uric acid, urea, glucose, magnesiu...