August, 1S41.] 60 



ous animals as strongly marked as in those of the viviparous 

 class. That they give a certain increased facility to parturition 

 is unquestionably true ; but their more uniform function is to sub- 

 serve the growth of bones, which they do by osseous deposition 

 at their margins ; hence a suture in the cranium is equivalent to 

 the surface which intervenes between the shaft and epiphysis of 

 a long bone. The latter grows in length by deposition at its ex- 

 tremities, and the epiphysis disappears, like the suture of the 

 cranium, when the growth of the bone is completed. 



Dr. Morton illustrated these views by means of the skull of a 

 mulatto boy who died when about eighteen years of age. In this 

 instance the sagittal suture is entirely wanting; in consequence of 

 which the lateral growth of the cranium has ceased in early in- 

 fancy, (no doubt when the suture became consolidated,) so that 

 the diameter between the parietal protuberances is less than 4.5 

 inches, instead of 5, which is about the negro average. The 

 squamous sutures, however, are fully open, whence the skull has 

 continued to expand in the upward direction until it has reached 

 the full vertical diameter of the negro, viz., 5.5 inches. The co- 

 ronal suture is also wanting, excepting some traces at its lower or 

 lateral extremities. The result of this deficiency is seen in the 

 very inadequate developement of the forehead, which is low and 

 narrow, but elongated below by means of the various craniofacial 

 sutures. The lambdoidal suture is complete, thus permitting of 

 posterior elongation ; and the growth in this direction, together 

 with the great vertical diameter already mentioned, has allowed 

 the brain to attain the bulk of seventy-seven cubic inches, or six 

 or eight inches short of the negro average- 



The growth of the brain and that of the skull are of course con- 

 sentaneous; nor is it probable, that either could be developed 

 without the sutures : hence there is reason to believe that the 

 absence of these may be a cause of idiocy, by preventing the 

 growth of the brain, and thus impairing or destroying its functions. 



Dr. Coates inclined to the opinion that, in cases similar to those 

 presented by Dr. Morton, the disappearance of the sutures was 

 rather to be regarded as a consequence than a cause ; and took 

 place, as in old age, because the necessity for further extension of 



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