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

Appendix: the 1555 ending to Chapter 15

The polemic against Galen which was originally in pp. 63-64, 65, and 67-68 of the 1543 edition was moved to the end of the chapter in the second edition with some additions and revisions. The new ending, covering the better part of four pages in the 1555 edition, is given here in its entirety.

Disagreements in this chapter with the writings of Galen

I would end the chapter at this point if my account of the cervical vertebrae were altogether in agreement with the writings of Galen. I will be silent about several places in which I could easily show from the space of the transverse processes of the first vertebra, 130 from the pathways that transmit branches of the first and second pair of nerves of the dorsal medulla, 131 from the perforation [foramen transversarium] of the seventh vertebra’s transverse process, and several other such instances, that Galen had described apes and dogs rather than humans in discussing those vertebrae. But I cannot pass over the fact that Galen feels much differently than I do about the motions of the head above the first vertebra, of the first vertebra [atlas] above the second [axis], and of the remaining cervical vertebrae. This must, indeed, be more carefully considered the more earnestly Galen demands a diligent, learned, clever, and hardworking listener who can take in what he says about the movements of the head in the twelfth book of De usu partium. What more can I say? He so strains the few who will understand what is explained there, and as it were deters the reader by the difficulty of his subject, especially one who is untrained in mathematics and the method of dissection, that everyone must try to illuminate his meaning and in this way observe with me whether I am rightly in such disagreement with his views.

Galen’s opinion about the motions of the head

Galen ascribes two motions to the head, teaching that one is made in nodding the head up and down, the other side to side. 132 He considers the first to be the one by which we flex the head forward, incline it, and nod, and next the one with which we bend the head backward [extension] and recline it in exactly that action with which the Turks and most Cretans even to the present day signify a negative. 133 When they do so they bend their head straight backward and raise it slightly; they do not rotate it from side to side or shake it as we do. By the other motion Galen means the one with which we incline the head to the side and move it as it were toward the shoulders or scapulae. You will learn his opinion about lateral and nodding motions from the fourth book of De anatomicis administrationibus if you pay close attention: what the point is where Galen states that the capitula of the occipital bone [condylus occipitalis] which are articulated to the first vertebra are located, protrude, and press when the head is moved to this side or that, and when, in Galen’s view, we nod it up and down. He declares that the motion of nodding up and down is accomplished by means of the second cervical vertebra, or above the second; and he says the other, by which the head moves to the sides, takes place above the first cervical vertebra. This may be quite readily learned from several places in Galen’s work, but especially in the fourth book of De anatomicis administrationibus. As he wrote that work last of all, he explained his view more concisely and expertly there than elsewhere. But you may now define the motions of the head quite differently from Galen and ask for yourself along with me whether that opinion of his was consonant with the truth.

A different opinion than Galen’s about the movements of the head

We move the head in the first kind of motion without moving the neck, / p. 85 / or in the second kind of motion when the head follows the motion of the neck even if you try to move it in a different direction than the neck is moved. There are two motions of the head alone. In the first, we flex it forward and incline or extend it backward; you perform this motion with the neck rigid and unmoving, or with the neck moved simultaneously whether you move it in the same motion as the head or in the opposite direction. However far you take the neck forward, the head necessarily follows the neck; but you can still bend the head backward in its own motion and easily observe at the same time that the neck and the head have their own distinct motions in bending separately forward and back. The other peculiar movement of the head should be counted the one by which we rotate it more or less as if we were spinning it as a wheel is turned on an axle. You will undergo this motion without moving the neck, whether you have tried to look left or right, or rotated the head. This motion is completely confined to the head: the neck does not have it. Therefore, however you move the neck, this rotation of the head is easily accomplished. For when the neck is bent and the head is inclined with it, you can easily move it in rotation. So even if the neck shall have been extended or moved sidewise to the shoulder, you can readily rotate the head. As the head possesses a single motion of rotation which the neck lacks, so the neck claims another motion peculiar to itself, by which it is moved to the side. The head has no motion of its own by which it is inclined to the side, but is moved to the side only by the neck and a secondary motion. Indeed, it is denied us to move the head even a little to this or that scapula except as taken that way by the neck. The head is endowed with its own motions, the first of which, consisting of flexion and reflexion, we have said is accomplished by means of the joint of the head with the first vertebra of the neck. 134 The second motion, by which the head is rotated, is accomplished above the second vertebra of the neck, as if on an axle. 135

The head is flexed back and forth on the first vertebra, but not from side to side or in any other way

It is my opinion therefore that the head is flexed and extended on the two joints of the head with the first vertebra, whether it is moved forward and back in the most direct motion. But by no account is it moved to the sides by their aid, though this had been stated by Galen in ever so many places. When the neck does not move, we are unable to move the head to the sides even a little. And if the head were moved to the side over the first vertebra, who doubts that the first vertebra would have to be kept immobile in that motion, if only because Aristotle rightly showed in On the Movements of Animals that one bone of a joint must be at rest when the joint moves? 136 Moreover, since the articulations of the first vertebra with the head are of such a kind that they cannot endure a small disarticulation or dislocation even for the smallest moment of time without a person being immediately deprived of respiration, speech, motion, and sense, as though the root of his nerves was affected, how could we join Galen and impute such negligence to Nature as to declare her so somnolent in the noblest joints of the entire body, as to require that the head of the bone which is moved needed to be raised out of the depression [facies articularis superior] by which it is articulated to another in such a way that it loses contact with the depression and is nowhere braced and planted upon it as we know all the other bones never depart or pull away from their socket in motions entrusted to them? For Galen decided that the head moves to the side over the first vertebra and was compelled to make the claim in the fourth book of De anatomicis administrationibus that when the head is moved to the right side, the right capitulum of the occipital bone is forced into the right depression of the first vertebra while the left capitulum rises out of the left depression, and the opposite whenever the head is inclined to the left side. We do not attribute a sidewise motion to this twin joint of the head with the first vertebra, but only a simple flexion and reflexion, and we are not inclined to pretend in defense of Galen that by motion to the sides he meant what I say is done in twisting and rotation. And we do not agree with Julius Pollux that rotation takes place over the first vertebra. For besides the fact that Galen did not mistake that motion for a lateral one, who is so stupid as to declare that the two separate oblong heads [condylus occipitalis] of the occipital bone fitting into the two deep, profound sockets [facies articularis superior] of the first vertebra, similarly oblong and separated from each other by a wide interval, could be rotated? Who ever saw a compass attached to a post by both legs move in a circle? It is impossible that someone hoping to defend Galen could imagine the heads of the occiput are pushed in flat upon themselves, and argue that the head is for this reason able to be rotated above the first vertebra. Among the other heads of bones Galen scarcely ever considered any worthy of the name korw/nh and took it only for these heads of the occiput which he calls by this name throughout 137 (though not quite correctly) — the same name he gives the rare points of the capitula of the occipital bone which occur in dogs rather than humans. So far as concerns the attachment of the first vertebra with the second, I am not at all able to agree with Galen that the head is flexed in any way by this joint and reclined backward.

The head and the first vertebra are rotated over the second vertebra, but not at all flexed and extended

For if you scrutinize individual features in the construction of these bones, the second vertebra of the neck will remind you of a beam set in the earth to which we have attached an axle. The dens will be this axle; and the first vertebra (to which the head is joined when swiveled in this motion as if they were a single body) will resemble a beam turned on the axle. The ligament running transversely over the dens [l. transversum atlantis] clearly shows that the first vertebra is in no way bent above the second: only if the dens were in abeyance could the first vertebra be moved in flexion forward and backward. Who then doubts that this ligament holds the dens in the depression [arcus anterior, fovea dentis] of the first vertebra, and that no such looseness could be ascribed to it (though that is what Galen does 138 ) that it should allow the first vertebra to be moved anteriorly so far from contact with the dens that the head would undergo true flexion? Further, two names in Julius Pollux now come to my support, one of which fits the first vertebra, the other the second. The first is named e)pistrofeu/j, the second its a)/cwn. These names undoubtedly have survived from the ancients, who trained their sons in anatomy. 139 They meant by the latter name to imply the vertebra which remains still like an axle, on which the other is swiveled as if on an axle; by the former they meant the vertebra which is turned about as on an axle. 140 Celsus (besides the poets) is my authority that these terms have survived from the ancients before Galen: though the portion of his book where he explains how the vertebra of the neck is damaged, and he himself altered things he did not understand, nevertheless he seems to have first taken that opinion which most closely approaches my own, and in fact truth itself, from some ancient source.

It is not possible for the head to be moved to the side over the first vertebra, nor even to be rotated

The reason why Nature wished only flexion and extension to be performed over the first vertebra but not two other motions, one to the sides and the other in rotation and turning (as the humerus and the femur are moved in three kinds of motion), 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 [foramen vertebrale], and that for that reason a single large, round depression could not be formed in it, nor indeed because of its own foramen [f. magnum] was the occipital bone able to swell out into a single head [condylus] so great that it could be moved in that depression [facies articularis superior] of the first vertebra with every type of motion as the femur is moved in the depression [acetabulum] of the bone of the hip [os coxae]. And so because the head had to be joined with a double joint, on the right and the left, and virtually the whole double joint [articulatio atlanto-occipitalis] performed only a simple motion, Nature justly wished that the head be flexed and extended over the first vertebra. 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 / p. 87 / of the occipital bone to be held in a single depression of the vertebra and another head strangely raised and quite dislocated from the first vertebra — though she is elsewhere 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. 141 Next, the head would still less 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 [cavitas cranii] 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 elegantly shaped. And so the head is rotated according to Nature's craft above the second vertebra [articulatio atlanto-axialis] for if it were bent there, the dens would tear the dorsal medulla.

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

Since in the absence of the dens the first vertebra would be moved downward, its posterior surface [arcus posterior atlantis] would be elevated and the dorsal medulla would then be squeezed and compressed 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 first deeply carved out on its anterior surface [fovea dentis] 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 be necessary for the first vertebra to be lifted a considerable distance above the second on one side, a danger that does not now threaten in rotation.

On what vertebrae lateral motion occurs

Nature imparted lateral motion to all the vertebrae of the neck with no ordinary diligence; these cannot be moved to the side separately and individually, but they are all inclined in that direction at the same time in successive motions so neatly that by their aid the head is conveniently borne to the side in a consequent motion without any harm.

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