The significance of the evolution of the cerebrospinal fluid system.

A study of the comparative morphology of the cerebrospinal fluid (CSF) system has been made in amphioxus, lamprey, dogfish, goldfish, lungfish, frog, salamander, turtle, pigeon, and mouse. Using mainly intracardiac fixation and a careful histological technique, serial sections have been obtained of the brain in situ surrounded by its various membranes and the skull. The ventricular system, the roof of the hindbrain, the meninges and subarachnoid space, the ependyma with its various derivatives, including the choroid plexuses and paraphysis, and the relationship between the various CSF compartments and the cerebrovascular system have all been compared in these animals. The hypothesis has been derived that the CSF system is primarily developed to maintain the chemical environment necessary to the function of the cells of the central nervous system, including the neuroendocrine pathways.