(Chapter 19) Footnote 32:

This section, omitted from the 1555 edition, continues Vesalius’ paraphrase of De usu partium, 3.600.16ff.; see May 1968, p. 380. Siraisi 1997 p. 11 points out that causal explanations of this kind diminish as one moves through the 1543 edition, and many, including the present instance, were systematically removed from the second edition.