THE SUTURES. 155 



of ossification will fill up these serrse; but when they are oblique, 

 the squamous suture will be subsequently formed. 



This theory also accounts for modes of junction intermediate 

 to the squamous and serrated suture ; for the formation of the 

 ossa Triquetra or Wormiana ; for their existence, form, size, and 

 number, in some skulls, and their total absence in others. The 

 inference will also be obvious, that in all ossifications from dif- 

 ferent nuclei, a suture will not be formed, where the membra- 

 nous partitions do not exist ; but that the bones will unite after 

 the manner of such as are fractured. We shall also understand, 

 that when these partitions are weak and imperfect, either from 

 their congenital condition, or from advanced age, as happens in 

 all sutures, but with some differences of time, the bones of the 

 opposite sides are fused together completely. 



The partitions which determine the places of the sutures, may 

 be demonstrated in a young adult skull by removing with mu- 

 riatic acid the calcareous portion of the bones, so as to leave 

 only the animal part. On opening the sutu/e after this process, 

 it will be seen, that the pericranium sends in its partition, which 

 is met by the partition coming from the dura mater. Or, if 

 either of these membranes be peeled off, its contribution of par- 

 tition will appear very plainly projecting from its surface, in 

 the form of a ridge. 



Owing to congenital hydrocephalus, the sutures of the vault 

 of the cranium have been known to remain open for years after 

 birth, from the continued augmentation of the volume of the 

 brain. In such cases additional bones are sometimes formed, 

 manifesting a strong attempt, on the part of nature, to cover the 

 brain with bone. I obtained, some years ago, a specimen of 

 this kind belonging to a foetus of nine months, whose head was 

 as large as it is commonly in adult life, and in whom there were 

 two ossa parietalia on one side. Morgagni,* whose authority 

 is proverbial in morbid anatomy, states, that a learned colleague 

 and intimate friend of his, Bernardin Rammazzani, aged seven- 

 ty, had the sutures open at that period of life. He does not say 

 at what time this condition of them appeared. I think it more 

 probable that they had never been closed, though Morgagni 



* Causes and Seats of Disease, Letter 3d, Art. 8th. 



