(Chapter 39) Footnote 37:

The 1555 edition adds: “But since the sacrum (no matter how straight you make the foramen hollowed in it for the dorsal medulla, using a knife, to run the iron rod through it) in this structure of bones that we are now preparing does not angle sufficiently to the posterior or face sufficiently downward to the pubic bone, it is my habit sometimes to carve a hole from the middle of the body of the second sacral bone (as if you made a hole from B in fig. 1, ch. 18 to a point above e in fig. 2 of the same chapter) straight up in the necessary place in the sacrum to the foramen of the dorsal medulla where it is situated in the highest part of the first sacral bone.” This would help to correct a distortion in Vesalius’ skeletons noted by Saunders and O’Malley (1950, p. 84) — and no doubt also by Vesalius’ contemporary critics — that “the spinal curvatures, fully recognized by Leonardo da Vinci, are virtually absent ... and the normal pelvic tilt is diminished.” Vesalius makes this concession to correct his tendency to minimize the complex curvatures of the spine and to show a single arcuate curve in the skeletons at the end of this Book. See Ch. 14, note 3. On Vesalius’ orientation of the pelvis, see Stromberg and Williams 1993.