(Chapter 27) Footnote 1:

This chapter’s sententious rhetoric and otherwise Galenic character (several sections are little more than translations from De usu partium), textual errors, and greater than usual obscurity of language invite the inference that it had been written earlier than the preceding chapters and sketchily revised for this book. Galen’s dithyramb on the hand as man’s distinguishing anatomical gift in the beginning of De usu partium (itself derived from a similar passage in Aristotle De part. an. 4.10.687a5 ff.) made the instruments of prehension a likely theme for Vesalius’ earliest writing. It was almost completely rewritten in the 1555 edition (see appendix at the end of this chapter), and is, with chapter 18, one of the two most extensively revised in Book I of the Fabrica.