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

Why Nature did not wish the head to be simultaneously rotated and inclined to the sides over the first vertebra.

The reason why Nature did not provide, in addition to forward and backward flexion, still two other motions, one toward the sides and the other in circular rotation, 90 above the first vertebra [articulatio atlanto-occipitalis], in the same way she wished the arm bone and the femur to be moved with three types of motion 91 you may infer is due especially to the fact that it was worthwhile for the first vertebra, being greater and wider than all the rest for the sake of the dorsal medulla, to be pierced (I in figs. 2 and 3) [foramen vertebrale], and that for that reason a single large, round socket could not be formed in it, nor indeed because of its own foramen (A in fig. 1) [f. magnum] was the occipital bone able to swell out into a single head so great that it could be moved in that socket [facies articularis superior] of the first vertebra with every type of motion as the femur is moved in the socket of the bone of the hip. And so because the head had to be attached with a double joint, on the right and the left, and virtually the whole double joint [articulationes zygapophysiales] performed only a simple motion, Nature justly wished that the head be flexed forward and back over the first vertebra [articulatio atlanto-occipitalis]. For it was unable to be moved to the side above this vertebra unless Nature were forgetful of herself here and had desired a single head of the occipital bone to be held in a single depression of the vertebra and another head raised and quite dislocated from the first vertebra, which she attempted in no joint, being ever mindful that the bones of the joint be in contact with each other and never separate or create some kind of unoccupied place invented by Galen. 92 Next, the head would not have been able to be rotated over the first vertebra unless Nature had put forth from the first vertebra an acute process into the head cavity where the brain is contained, a process on which the head would be turned as on an axis, and unless, finally, she had intended to vitiate many other things now quite rightly shaped. And so the head is rotated


page 68

according to Nature’s craft above the second vertebra [articulatio atlanto-axialis mediana]; for if it were bent there, the dens would break the dorsal medulla.



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