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ponding part of the cranium. On t1ie other hand, the base of 

 the brain, where the orig in of all the nei-ves is situated, requires 

 more secure means of defence; hence the corresponding part of 

 the cranium has its structure, on which its powers of defence 

 depend, rapidly developed. 



In the cranium of a toetus at birth, we remark two beautiful 

 arrangements, destined, at the same tinie, to facilitate the process 

 of parturition, and to protect that part of the brain, which more 

 particularly requires defence. Ossification has, at this period, as 

 I have already remarked, so far advanced in the base, that almost all 

 the bones are contiguous ; and, where there is any interval between 

 their edges, it is filled by a cartilage having considerable powers 

 ot resistence. At the same period, the bones of the vault are se- 

 parated, to a considerable extent, from each other, and only united 

 by membranes. This conformation gives to the base a great de- 

 gree of strength, and enables it to resist any pressure, which would 

 be likely to alter its form, and thereby injure a portion of the brain, 

 very sensible to every mechanical violence ; while the Jjones of the 

 vault are enabled to approximate, and even to overlap each other : 

 a change, which, in consequence of the structure of this part of 

 the brain, can take place with impunity. From all these consi- 

 derations it appears, that it is by alterations in the form of the vault, 

 and more particularly of its anterior part, that tlie head accommo- 

 dates itself to the form of the pelvis during parturition. 



After birth, the bones extend themselves to such a degree, as, 

 not only to increase the dimensions of the cranium, but also to 

 approach each other ; and thereby diminish or aimihilate the inter- 

 vals, which separated them in earlier life. At last they iiave ar- 

 rived at such a state, that t!iey are almost every where in contact; 

 and we remark, that their edges have then assumed forms of va- 



