]45 



rious kinds, preparatory to their union with each other. Those 

 bones, which are in the base, have plane ed^es ;* those on the sides 

 of the vault are so constructed, that one bone shall overlap the 

 other ;-f those on the top of the vault are serrated, by which they 

 are mutually enabled to receive and support one another.;}; It will 

 be admitted, that the cause of all these peculiarities has never been 

 satisfactorily explained. Some Physiologists, unable to conceive 

 the possibility of any occurrence in the body, without a mechanical 

 cause, have attempted to account for the phenomena on mecha- 

 nical principles. By them we are told, that the bones of the cra- 

 nium overlap each other at the side, in consequence of the pres- 

 sure of the temporal muscle ;§ and that the conformation of their 

 edges in the top of the vault, where they are serrated, arises from 

 the bones ossifying in the form of radii, and hence mutually re- 

 ceiving each other, when they meet.^f Their opinion is, however, 

 proved to be without foundation, when it is considered. 



First, that the overlapping of the bones of the cranium is to be 

 observed, where neither the pressure of the temporal muscle, nor any 

 mechanical agency, with which we are acquainted, can exist- 



VOL. XIII. X 



* Harmonia. f Sutura squamosa. J Sutura vera; 



f The manner how I imagine this sort of suture is formed at these places is, that, by the 

 action of the strong temporal muscles on one side, and by the pressure of the brain on the other, 

 the bones are made so thin, that they have not large enough surfaces opposed to each other 

 to stsp the extention of their fibres in length, and thus to cause the common serrated appear- 

 ance of sutures, but the narrow edge of one bone slides over the other. Monro's Works, 

 edited by his Son, p. 75. 



^ " The suture is that articulation, where two bones are mutually indented into each other, 

 or as if they were sewed together ; and is formed by the fibres of two bones meeting, while 

 they are yet flexible and yielding, and have not come to their full extent of growth : so that 

 they mutually force into the interstices of each other." Monro's Works, edited by his Son, 

 p. 55— »6. 



