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 6 On the Eight Bones of the Head and the Sutures Connecting Them

Why the skull is not made of solid bone. 42

But because the head resembles the roof of a warm house, receiving whatever smoky and vaporous wastes of the parts below that ascend upwards, 43 and consequently the head itself needs a more plentiful means of evacuation, the wise Parent of things shaped a helmet for the brain that is not solid everywhere but full of hollows 44 and laced with sutures (figs. 1 and 2), not piercing the face everywhere like a sponge with small and uneven foramina like little cavities: rather, he wished the little cavities to end on each side, inside and out (ai, ei, oi in fig. 2 and the character & in fig. 6), in a smooth, dense scale of bone, because they would meet on one side the hard membrane of the brain [dura mater] and on the other the membrane surrounding the skull which is called perikra/nioj. 45 For if the entire substance of the skull remained porous, and the pores were covered by no cortex, the bone’s roughness would abrade and damage things near it. Moreover, if it were entirely porous and spongy, it would have no strength, and would be weak and fragile, like pumice. Perhaps someone will think there is no reason why the bone of the skull between the two scales is porous and full of cavities, 46 since the abundance and size of its sutures require no further assistance in transpiration. So if as this person judged preferable the entire skull were at once thin, dense, and solid, the construction of the organs lying beneath would be rendered no safer by this means, since things that injure bones would be able to penetrate inside quickly because the distance to be traveled would be so short. But if the skull were created at once thick and dense without any kind of pores, the resulting weight would be no different than if a person were compelled constantly to carry a knapsack on his head. The third recourse therefore was for the bone of the skull to be constructed neither thin nor dense or solid, but thick, loose-knit, and porous. 47 Thus it would not be too heavy, nor would there be a short path into the brain for things striking through it.



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 6 On the Eight Bones of the Head and the Sutures Connecting Them