CRANIUM. 



745 



There are but few skulls which are perfectly 

 symmetrical, although the variation of one side 

 from the other is generally so slight that the eye 

 does not at once detect it. In numerous cases, 

 however, the want of symmetry forcibly obtrudes 

 itself; sometimes one half is considerably larger 

 than the other ; and in other cases it appears 

 to be thrown out of position, as though, during 

 the time that the parietes were soft, pressure 

 had been applied in front and behind, and, by 

 a sort of rotatory movement, it had been drawn 

 back on one side and pushed forward on the 

 opposite. There does not appear to be an 

 absolute uniformity among the skulls of this 

 description saving that the projections are 

 always situated diagonally with respect to each 

 other ; that is, if it be twisted to the right, the 

 right half of the frontal bone will be in advance 

 of the left ; while the posterior part of the left 

 parietal, and the corresponding side of the 

 occipital bone, will project behind the right. 

 This is by far the most prevalent variation, but, 

 occasionally, the left half of the frontal bone is 

 in advance, and, in such instances, the posterior 

 increase will be on the right side. 



The change which takes place in advanced 

 age can scarcely be accounted an anomaly. At 

 that period the skull is much more an entire 

 bone than it is in the earlier epochs. The 

 sutures are to a certain extent effaced, and a 

 mere line indicates the former disjunction of 

 the bones. It is on the interior of the skull 

 that these sutures are first effaced, and on the 

 exterior the order of obliteration is from the 

 summit to the base. It has been affirmed that 

 the volume of the skull diminishes in old age, 

 and that it is susceptible of change, in different 

 directions, after the bones are locked together. 

 It is, however, certain that its external con- 

 figuration is somewhat altered, for the promi- 

 nences formed by the centres of ossification of 

 the parietal and frontal bones become flattened 

 and undistinguishable from the rest of the 

 parietes; which, as old age sets in, become 

 thinner than they were previously. This change, 

 however, is but temporary, for, in extreme old 

 age, the skull is thicker and more porous than 

 at any antecedent period of life. This hyper- 

 trophy is produced by the recession of the 

 inner from the outer table, and the conversion 

 of some part of the substance of each into a 

 thin spongy tissue ; the diploe itself sustaining 

 an analogous alteration, by the enlargement of 

 its cells, and the thinning of the plates which 

 form their walls. 



Occasional instances occur in which the 

 skull is of inordinate thickness, and this, appa- 

 rently, without its being connected with the 

 age of the subject. The late Mr. Joshua Brookes 

 had some sections of a skull, found in a church- 

 yard in Lancashire, of nearly three quarters of 

 an inch in thickness; and specimens have been 

 seen of more than an inch. In some of them 

 the diploe is perfect, the augmentation being in 

 the two tables ; in others, and indeed in the 

 majority of specimens, the two tables and the 

 dipliie are confounded together in one thick 

 mass of matter, which is of an ivory hardness. It 

 is not improbable that we might justly refer this 



condition, as well as some other peculiarities of 

 the cranium, to inflammation of the bone itself, 

 or of its investing membranes. That exostosis 

 is the product of a limited periostitis admits of 

 but little dispute, and it is very likely that those 

 cases of hyperostosis in which there is a uniform 

 deposit of bone, only mark the effect of a more 

 diffused and general inflammation; the more 

 so, since we meet with these local and general 

 deposits, as well on the inner, as on the outer 

 table of the skull, and for the existence of which 

 it would otherwise be impossible to account. 



When they occur on the inner table, the func- 

 tions of the brain are usually more or less dis- 

 turbed, although it would appear that the mental 

 manifestations are not always implicated. In 

 the skull of an idiot of advanced age, examined 

 several years since by the writer of this article, 

 there was a uniform deposition to the extent of 

 nearly a quarter of an inch ; and in arecent autopsy 

 of a young girl, he found the entire syncipital 

 region very irregular in its surface, from being 

 studded with variously-sized nodules, the bases 

 of which flowed into and were lost in each other. 

 This girl was of feeble intellect, and the victim 

 of epilepsy. In the examination of a body at 

 the Hotel Dieu, by Mr. King, that gentleman 

 discovered on the petrous portion of the tem- 

 poral bone a tumour which he had not been led 

 to expect by any indication of suffering which 

 appeared during life. This tumour had the 

 volume of a marble or pistol-bullet, was cel- 

 lular in its structure, and perfectly smooth on 

 its surface ; a depression exactly corresponding 

 to it was found on the under surface of the 

 middle lobe of the brain, but its substance and 

 membranes had their normal characters. 



The cranium is oftentimes found in the oppo- 

 site state of atrophy, in which the balance be- 

 tween deposition and absorption seems to have 

 been disturbed, so much to the prejudice of 

 the former, that the walls are sometimes not 

 much thicker than a piece of paper. When- 

 ever the two textures maintain their usual pro- 

 portion, this atrophy may be regarded as a 

 natural abnormal state; but those cases in 

 which either the inorganic or animal element 

 preponderates, and a fragility or softening of 

 the bone is thereby established, must be referred 

 to some constitutional affection in which the 

 rest of the osseous system has participated, 

 and the influence of which it will not fail to 

 exhibit. 



In addition to exostosis and hyperostosis, the 

 cranium sustains other pathological changes as 

 the effects of inflammation. 



Previously to the establishment of osteitis, 

 whether from a common or specific cause, 

 mercurial or syphilitic, there is found that stasis 

 of the blood which always precedes inflam- 

 mation. The sanguineous complexion of the 

 diploe in cases of erysipelas testifies that this 

 engorgement may be produced by increased 

 action in the neighbouring teguments. 



It has already been stated that hypertrophy 

 of the cranium may be regarded as a termina- 

 tion of osteitis. When inflammation is limited 

 in its action and of long duration, it is probable 

 that the ossific element is poured into the cells 



VOL. I. 



