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 29 On the Bones Which Are Attached to the Sides of the Sacrum

The surface of the ilium attached to the sacrum

First, the area of the ilium attached to the sacrum (A, B, C, D, E, F, G in figure 3) [facies sacropelvica, f. auricularis] is especially varied, as we have said the transverse processes of the sacrum are varied and complex at the point [pars lateralis, facies auricularis] where they are joined to the iliac bones. The convex parts [facies sacropelvica] of the ilium will match individual depressions of those processes, and its depressions will match the convexities of the same processes in such a way that the ilium is joined to the sacrum by the mutual fit of their various parts: not indeed with a connection built for voluntary motion, or with smooth depressions and convexities coated with slippery cartilage, but with a very powerful bond comparable to a type of symphysis or union. 27 This is accomplished by means of cartilaginous ligament, or rather pure cartilage. 28 The shape of the depressions and projections by which the ilium is attached to the sacrum is easily discovered from the description of the sacrum. As it was first stated that the transverse processes of the sacrum are equipped with a long depression, so too the ilium has a long projection (C, C in fig. 3; compare in order with fig. 2, ch. 18) [facies auricularis] that matches the depression; and because the anterior part or brow of the depression of the processes protrudes and extends quite markedly, there are also carved in the ilium, close to the anterior surface of its long ridge, depressions (A, B in fig. 3) which those protruding parts enter. When the lowest part of these depressions (B in fig. 3) is viewed, the ilium becomes sharp like a knife [spina iliaca posterior inferior] so that it makes a single surface with the transverse process [pars lateralis] (the lower L in fig. 2, ch. 18) of the fourth bone of the sacrum. In turn, the long depression of the ilium (D, D in fig. 3) fits and precisely admits the long ridge of the sacrum, which we have said stands out like a spine 29 in the depressions of the processes. The iliac bone (E, F, G in fig. 3) [tuberositas iliaca] does not as perfectly match the two depressions of the processes by the posterior end of the ridge just mentioned, and the ridge protruding transversely between the depressions, 30 since it does not protrude as high as the depressions of the processes are carved deep. Nor does the iliac bone provide a place to receive the ridge between those depressions. In a word, the sacrum is not quite conterminous with the ilium in the area where those two depressions of the processes of the sacrum are seen, but a very large cartilage 31 participating in the nature of a ligament 32 comes between these bones and packs the entire space where the bones are separated. The entire surface of the ilium that is attached to the sacrum is rough, uneven, and quite thick, as we know other bones are wide and thick in the areas where they are attached to each other so as to effect a stronger and broader bond.



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 29 On the Bones Which Are Attached to the Sides of the Sacrum