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 18 On the Sacral Bone and the Coccyx

An account of the coccyx

The coccyx (G, H, I, K in figs. 1 and 3; I, K in the fig. for ch. 14, N in the skeletons) is constructed of four ossicles, the topmost of which forms a depression in which is received the tubercle [apex ossis sacri] of the sixth sacral bone (F in fig. 1), which is attached to it in the manner of vertebral bodies by a quite cartilaginous ligament [discus intervertebralis], but without any other kind of articulation, save in cases where the sacrum is made of only five bones. To provide in such cases for the construction of a foramen in the posterior side, and to bring down and protect a nerve of the sixth sacral pair, this first bone puts out in its posterior side two small, sharp processes [cornu coccygeum] which face upward and form a strong bond with the processes of the fifth sacral bone. The first ossicle of the coccyx itself is joined with the fifth sacral bone scarcely at all by cartilaginous ligament, but virtually fuses with it like the bones of the sacrum. When there are six bones in the sacrum (which happens most often), 41 the first bone of the coccyx puts forth no such processes. 42 At the sides of the depression by which it is joined to the sixth bone of the sacrum, it widens transversely [processus transversus] in its upper portion but narrows gradually in its lower portion, and in turn is joined to the second bone (lower b [discus intervertebralis] in fig. 2) exactly as we said it is joined to the sixth bone of the sacrum. The third and fourth bones follow, attached to each other in quite the same manner, and as much smaller the lower the place in the series each takes. No foramen [canalis centralis] is ever carved


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in these ossicles for the dorsal medulla to continue its course, or for any nerves to go out. The spinal medulla terminates in the sixth bone of the sacrum, and its end (56 in figs. 2, 3, ch. 11, Bk. 4) [filum terminale] does not go down into the coccyx. These ossicles are spongy, reddish like the breastbone [sternum], and in children quite cartilaginous. They taper overall from a rather broad base to a point and are curved inward like the beak of a cuckoo. The lowest ossicle reverts into cartilage at its point (c in figures 2 and 3), where it touches the rear and lowest point of the straight intestine (a in fig. 8, Bk. 5) [rectum], for the same purpose that we have stated cartilage grows on the spines of the vertebrae.



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 18 On the Sacral Bone and the Coccyx