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formed, at an earlier period, the medium of connexion between the 

 edges of the bones in the vault, is converted into a membrane much 

 thicker, more unyielding, of a fibrous structure, and resembling more 

 nearly the texture of a very strong fibrous membrane, than any 

 other tissue in the body. At the same period, the cartilage, which 

 joined the bones in the base, is less in quantity, the bones being now 

 more closely applied to each other ; and it has assumed the appear- 

 ance of fibro-cartilage. If the cranium be examined, when its de- 

 velopment is a little farther advanced, the edges of the bones are so 

 closely applied to each other, that no medium of connexion is ob- 

 servable ; hence the cause of anatomists remaining so long ignorant 

 of the existence of an animal substance, between the edges of the 

 bones of the cranium, when their articulations are perfectly formed.* 

 From observing the state of these articulations at the earlier periods 

 of life, I was led to suspect, that, even when they are most perfect, 

 there exists between the bones, that form them, an animal substance; 

 and I was able, by the following simple process, to demonstrate, not 

 only its existence, but also its nature. I deprived a recent cranium 

 of its soft coverings, and subjected it to the action of dilute muriatic 

 acid, with the intention of examing the nature of this medium ; 

 which I expected to be able to do, by depriving the bones of their 

 calcareous matter. The cranium had not been long exposed to the 

 acid, when it was rendered flexible, and appeared formed of one con- 

 tinuous sheet of cartilage. The cartilagenous basis of all the bones 

 of this cavity is therefore continuous, there being no interruption, as 

 is generally supposed, where these bones are articulated together. 

 Thus we observe, that, when the articulations of the bones of the cra- 

 nium are perfectly formed, there is a cartilaginous medium of union, 

 which serves to keep the bones, which form the cavity, in contact ; 

 and this cartilaginous medium is, at this period, continuous and of 



• Bichat, Anatoniie descriptive. 



