(Chapter 6) Footnote 17:

The part numbered 2 and 5 is lamina lateralis processus pterygoidei; 3 and 4 is lamina medialis processus pterygoidei. Also illustrated, although unlabeled on the right side of the drawing (left base of skull), is the foramen of Vesalius, foramen emissaria, which appears just anterio-medial to foramen ovale (labeled Q) on the lateral side of the scaphoid fossa; this inconstant foramen transmits a small emissary vein from the cavernous sinus to the pterygoid plexus.