(Chapter 21) Footnote 73:

On fracture or avulsion of the acromion, see De articulis 13 and Vectiarius 6. It is difficult to follow what Vesalius’ point here is if we look for it in the Hippocratic works cited. The Greek term acromion indicates only that it is the tip of the process that bears it. Vesalius is perhaps thinking not of anything in Hippocrates but rather of a passage in the thirteenth book of De usu partium (4.122.1ff.) where Galen states that the “acromion” or acromioclavicular articulation was formed by Nature “to be a covering and protection for the enarthrosis at the shoulder and at the same time to prevent the head of the humerus from being dislocated upward and keep the scapula itself from separating forthwith from the thorax.” (tr. May 1968, p. 609). The point is important to Vesalius because it reinforces the multiple teleology that he follows Galen in ascribing to Nature.