8 And who could possibly trace out all the wisdom which is manifested by means of the brain! For, in the first place, He made it soft, since it serves as a fountain to all the senses. Next, in order that it might not suffer injury owing to its peculiar nature, He fortified it on every side with bones. Further; that it might not suffer from friction, by the hardness of the bones, He interposed a middle membrane: and not only a single one, but also a second; the former being spread out on the under side of the skull, but the latter enveloping the upper substance of the brain, and the first being the harder of the two.
And this was done, both for the cause that has been mentioned, and in order that the brain might not be the first to receive the blows inflicted upon the head; but that these membranes first encountering them, might free it from all injury, and preserve it unwounded. Moreover, that the bone which covers the brain is not a single and continuous one, but has many sutures on every side, is a circumstance which contributes much to its security. For a ventilation of the vapours that surround it may easily take place outward through these sutures, so as to prevent it from being suffocated; and if a blow should be inflicted upon it, on any particular point, the damage does not extend to the whole.
For if the bone had been one and continuous, the stroke even when it fell upon one part, only, would have injured the whole; but now, by its being divided into many parts, this can never happen. For if one part should chance to be wounded, only the bone that is situated near that part receives injury, but all the rest remain unhurt; the continuity of the stroke being intercepted by the division of the bones, and being unable to extend itself to the adjacent parts. By reason of this God has constructed a covering for the brain of many bones; and just as when one builds a house, he lays on a roof, and tiles upon the upper part, so God has placed these bones above upon the head, and has provided that the hairs should shoot forth, and serve as a kind of cap for it.
Source: Homilies on the Statues (New Advent)