(Chapter 39) Footnote 39:

The preceding sentences, beginning “When the rod has been fitted perpendicularly in the round base,” outline a procedure which results in the diminished pelvic tilt noted by Saunders and O’Malley. They are omitted in the 1555 edition, where the present sentence begins “When the sacrum, with the iliac bones attached to it on each side as we have just said, has been supported on the iron rod that is fixed in the round base, ...”