Footnote 19:

Identified by C.D. O’Malley as Gerard van Veltwyck, c. 1505-1555, a member of the emperor’s privy council; see Vocht 1951-55, III p. 555-358. Veltwyck was a fellow student with Vesalius at the Castle School in Louvain; see O’Malley, AVB pp. 31, 275. He is mentioned again in the Letter on the China Root, p. 19. This reference to his friend is deleted from the 1555 edition as a consequence of Veltwyck’s death in January, 1555.