(Chapter 12) Footnote 47:

Vesalius cites book 9 of De usu partium, where see 3.694.4ff., May 1968, pp. 429f. and n. 7: “The sella turcica of the cuneiform bone [os sphenoidale] is pierced by foramina for blood vessels, and Galen may have thought that the residues descended through these into the body of the sphenoid. Galenic physiology maintained that the brain was purged of its residues by phlegm.” See also note 19 above.