In its mode of origin and in its pathways of absorption, as well as in its physical and chemical properties, the cerebrospinal fluid is unique among the body fluids. Two facts derived from clinical and experimental observations have been established within recent years with a fair degree of conclusiveness, namely, the dual origin of the cerebrospinal fluid and its return to the general circulation chiefly by a process of filtration through the arachnoid villi into the great sinuses.1,2 Unlike the circulating lymph, which is derived from the blood by a process of filtration, diffusion and osmosis, the cerebrospinal fluid is the secretory product of the ependymal cells which cover the choroid plexuses, although it must be admitted that certain fundamental anatomic and physiologic aspects of this problem are still unsolved.
Another interesting observation which has been brought forth by a number of workers is that these
HURWITZ SH, TRANTER CL. ON THE REACTION OF THE CEREBROSPINAL FLUID. Arch Intern Med (Chic). 1916;XVII(6_1):828-839. doi:10.1001/archinte.1916.00080120119006