(Chapter 24) Footnote 43:

Correctly, the proximal end. As in his illustrations, Vesalius describes the forearm with the elbow down and the hand raised so that “lower” becomes the elbow. But in this he is inconsistent, for a sentence or two later he describes the posterior border of the ulna running “downward,” deorsum, toward the wrist. Thereafter “upper” usually = distal and “lower” usually = proximal, but caveat lector.