In the beginning of the sixteenth century, anatomy made great progress and at least two developments took place that are important from our point of view. First, Niccolò Massa (1536, ch. 38) discovered that the ventricles are not filled with some airy or vaporous spirit but with fluid (the liquor cerebro-spinalis). Second, Andreas Vesalius (1543, book 7) rejected all ventricular localization theories and all theories according to which the choroid plexus, pineal gland or vermis of the cerebellum can regulate the flow of spirits in the ventricles of the brain.