Use of the Sutures in the Skulls of Animals. 239 



in bone, the addition is still made at the edge of each, and 

 that the general enlargement originates where they are all 

 mutually joined by the sutures. Of this process I had a very 

 striking illustration some years ago. In h young subject^ 

 from what cause I know not, the deposition of osseous 

 matter had been suddenly increased a short time beforedeath. 

 It was in diflcrent stages of progress, but had taken place in 

 all the bones of the bodv which I preserved ; in some par- 

 tially, in others generally. In all, the new osseous matter 

 was elevated above the level of the bone, upon which it was 

 placed. In some parts of the parietal bones it was only in 

 its conunencemtnt, and put on the appearance of a net- 

 work, .'similar to that which may be observed in the same 

 bones at an early period of their formation. In other parts 

 the meshes of the net-work were more or less filled up ; in 

 others again completely, so as to put on the uniform appear-* 

 ance of solid bone. The same reticulated appearance was 

 evident on the edges of all the bones of the skull, where 

 they form the sutures, and at the extremities of the cylindri- 

 cal bones, between the body and epiphysis. The same ap- 

 pearance of increased deposition was seen on the surface of 

 ihe cylindrical bones, with this difference, that the meshes 

 were not circular, but oblong squares ; so as to put on more 

 of the striated appearance. In some parts, the newly 

 secreted bone was easily separable from the general mass, 

 and formed a thin layer externally, affording one of the best 

 proofs I have met with, of the increase of cylindrical bone* 

 in thickness by deposition externally, whilst a corresponding 

 internal absorption goes on. From the striking similarity 

 of appearance on the surfaces and edges of the bones, wc 

 may safely conclude, that the same process of deposition 

 was going on in both, and may thence infer, that the bones 

 of the skull are increased in extent by the deposition of 

 osseous matter at their edges, or where they arc joined to 

 each other by suture. Tliis fact points out to us, in a great 

 measure, the real use of this peculiar mode of junction. 



In order that the bones of the skull may be increased ia 

 extent, it is necessary that tbey should be retained at a cer- 

 tain distance from each otlier; that the. periosteum with its 



i\ 2 vessels 



