Does the secretion and circulation of the cerebrospinal fluid really exist?

The secretion and circulation of cerebrospinal fluid have been studied in anaesthetized cats by means of a plastic cannula introduced into the aqueduct of Sylvius and by inspection of free escape of cerebrospinal fluid out of the end of the cannula. The fact that during the 120-minute period of observation not a single drop of CSF escaped out of the cannula, at physiological pressure, indicates that cerebrospinal fluid does neither secrete nor circulate.