28 SURGICAL APPLIED ANATOMY. [Chap. IL 



Separation of sutures. This condition, as the 

 result of injury, is practically restricted to the young 

 skull. In later life, force applied at the site of an 

 obliterated suture may cause a fracture, which accu 

 rately follows the old suture line. Separation of the 

 sutures, independent of fracture, is very rare in the 

 adult skull. In the few instances of such a condition 

 the temporal bone has usually been the one displaced, 

 and the separation noted at the squamous suture. 

 When associated with fracture, the coronal and 

 sagittal sutures are those most frequently separated, 

 and next in frequency the lambdoid. 



The thickness of the skull cap varies greatly, 

 not only in different parts of the same skull, but also 

 in corresponding parts in different individuals. The 

 average thickness is one-fifth of an inch. The thickest 

 parts are at the occipital protuberance (where the 

 section may measure half an inch), the mastoid pro- 

 cess, and the lower part of the frontal bone. The 

 bone over the inferior occipital fossae is very thin, 

 while it is thinnest over the squamous bone. Here 

 the bone may be no thicker in parts than a visiting 

 card. The skull is also thinned over the sinuses and 

 grooves for the meningeal vessels. It is especially 

 thin over the anterior inferior angle of the parietal 

 bone. It is important to remember in trephining that 

 the inner table is not always parallel with the outer. 



Craniectomy. This operation is carried out in 

 cases of microcephaly in infants and children. It 

 consists in the removal of a strip of bone from the 

 vertex of the skull so as to give to the brain, as an 

 American author expresses it, "more elbow room." 



