The anatomy of the meningeal-choroidal complex, or, as it may conveniently be termed, the subarachnoid system, is quite well understood: its physiology and pathology are shrouded in a large measure of uncertainty, while recognition of its clinical importance is recent and, even yet, not very general.
For a summary and an extension of our knowledge of the development, structure and function of this part of the envelop of the central nervous system, we are indebted to Weed,1 to whose writings the reader is referred for details and the literature
It seems to be established that the cerebrospinal fluid is largely a product of the choroid plexus of the cerebral ventricles, with small, probably insignificant, accretions from the general ependymal cells and the capillaries of nervous tissue itself, through their perivascular channels; that it exists in an amount of from 60 to 150 c.c., and that its formation is rapid