Section I. of the Skull.

=Fracture.= In a post-mortem examination of the head, after death from a blow or fall upon that part, a fracture may be disclosed of which there was no external trace. Owing to the greater thinness and brittleness of the inner table, it is possible for this to be fractured without any corresponding injury to the external; such fracture may possibly rupture some of the branches of the meningeal arteries, which will be followed by the formation of a clot between the bone and dura mater, the pressure of which may be sufficient to produce death. Owing to the same cause—greater brittleness of the inner table—when fracture of the outer exists, that of the inner table will be likely to be more extensive, accompanied perhaps with depression, of which there is no external evidence.

Again, it will sometimes be discovered that fracture exists at a point opposite to that upon which the blow was received, on the principle of the “contre coup” of the French; thus, the blow having been received on the occiput, the fracture may be found in the frontal region; or, received on the top of the skull, fracture may result at the base. In falls from a height, upon the top of the head, the weight of the body, acting through the cervical vertebræ as a propelling force, is very likely to produce fracture of the occipital bone.

=Caries= may affect any of the bones of the head, but in the majority of cases it will be the result of syphilitic or mercurial poisoning. Following an attack of periostitis, the inflammation extends to the bone and gradually develops the carious ulceration. While the condition is usually confined to, or at least, most strongly developed upon the outer table, it may involve the entire thickness. In syphilitic ulceration of the bones of the nasal cavity, the disease may destroy the cribriform plate of the ethmoid bone, and thus extend to the membranes of the brain. So also, in caries of the petrous and mastoid portions of the temporal bone, which sometimes results from scarlet fever, the disease may extend to the inner surface, resulting in the accumulation of pus within the cranial cavity.

Along either side of the central portion of the inner surface of the calvarium may be usually seen, at least in the heads of aged persons, a number of irregular, rough pits, varying in size and depth, which are not to be mistaken for disease of the bone, they being simply impressions of the Pacchionian glands.

=Thinning= of the bones of the head will always indicate increased pressure from within, induced by hypertrophy of the brain, or, as is more frequent, hydrocephalus. In the latter case, not only thinning, but complete absorption of the parietal and other bones may result.

=Increased Thickness= will also sometimes be found. This condition indicates diminished pressure from within, as in atrophy of the brain. The thickening results from a gradual remodeling of the inner table and diploe, so that while the exterior of the skull may retain its normal size and form, the inner table following the retiring and shrinking brain, the interval between the two becomes filled with the thickened diploe. It has been observed that this hypertrophy is greatest at those parts of the bones where ossification first commences, as at the parietal and frontal eminences. It is not confined to old persons, though perhaps more frequent with them.