Book One -- The things that sustain and support the entire body, and what braces and attaches them all. [the bones and the ligaments that interconnect them] | Chapter 15 On the Vertebrae of the Neck or Cervix

The head cannot be flexed forward and back over the second vertebra, nor be inclined to the side.

For if the first vertebra were moved forward and raised above its posterior seat without movement of the dens, the dorsal medulla would then be altogether squeezed and crushed in the foramen of the first vertebra, and would be torn away. Also the first vertebra could in no way be flexed backward over the second unless it were itself deeply carved out on its anterior surface (K, L in figures 3 and 4) where it holds the dens, and the first vertebra, not obstructed by the dens, would freely be moved backward. Moreover, the head could in no way be moved toward the side above the second vertebra for the same reason we have proved that lateral motion is impossible over the first. Otherwise it would always be necessary for the first vertebra to be lifted from the second on one side, a danger that does not now threaten from rotation.



Book One -- The things that sustain and support the entire body, and what braces and attaches them all. [the bones and the ligaments that interconnect them] | Chapter 15 On the Vertebrae of the Neck or Cervix