Page:Transactions of the Provincial Medical and Surgical Association, volume 1.djvu/88

 seems merely destined to promote its elasticity; and its elasticity is of the greatest service in diffusing local percussion, and thereby lessening the effect from external injuries upon the inner table and brain. By transmitting small blood-vessels in both directions, it merely performs another part of its connecting function.

We come now to the outer table. It is every where separated from the inner table by the diploë, except at the frontal sinus, and in the ethmoid, sphenoid, and basilar portion of the occipital bones, where it is generally formed into sinuses lined with a mucous membrane. The diploë, it is well known, contains no such membrane.

Considered in relation to the brain, the membranes, the inner table, and the diploë itself, the outer table presents no other definite organization beyond that of an irregular envelope, which is in some places as thin as a wafer, in others thicker than all the rest of the cranium. But, if we view it from without, we find that every particle of its surface is adapted to some purpose which it has to answer in combination with the soft parts with which it is in contact. Many processes are levers for the muscles; others are merely scabrous surfaces for their insertion; others are condyles for joints; others, organs of hearing; others, organs of fixation; others, of protection; and all this in direct reference to the organs in contact, but without the least relation, that can be discovered, to the encephalon. Hence we are forced to conclude that its projections solely originate under the influence, and for the completion of, functions that are all external