(Chapter 30) Footnote 33:

Vesalius is probably referring to the inguinal lymph nodes situated in the upper part of the femoral triangle. If so, he is, like Galen, taking lymphatic vessels for blood vessels. See for example De usu partium 3.335.14ff. (May 1968, p. 242): “First, throughout the mesentery [nature] created special veins [lymphatic vessels] which are devoted to the nourishment of the intestines themselves . . . For as Herophilus, too, says, these veins terminate in certain glandular bodies [sc. lymphatic glands of the mesentery], although all the other veins proceed upward to the porta.” (tr. von Staden 1989, p. 226). The human lymphatic system was first demonstrated by Thomas Bartholin in 1652.