chap. iL] BONY VAULT OF THE CRANIUM. 17 



bone. An interfibrillar space, larger than the rest, is 

 seen about the fifth month to separate the loose osseous 

 fibres which abut on the posterior part of the sagittal 

 border from the stronger fibres which form the rest of 

 this border (Pozzi). This is the parietal fissure. It 

 usually closes and leaves no trace, but it may persist 

 in part as a suture-like fissure, and be mistaken for a 

 fracture (Fig. 4 B). If the fissure persists equally on 

 the two sides an elongated lozenge-shaped gap is left, 

 the sagittal fontanelle. It is situate about an inch 

 in front of the lambda (Fig. 4 c). 



Necrosis is fairly common on the vault of the 

 skull, and most often attacks the frontal and parietal 

 bones, while, for reasons that are not very obvious, it 

 is rare in the occipital bone. The external table is 

 frequently necrosed alone, it being more exposed to 

 injury and less amply supplied with blood than is the 

 internal table. From the converse of these reasons 

 it happens that necrosis of the internal table alone is 

 but rarely met with. Necrosis involving the entire 

 thickness of the bone may prove very extensive, and 

 in a case reported by Saviardj practically the whole of 

 the cranial vault necrosed and came away. The 

 patient was a woman, and the primary cause of the 

 mischief was a fall upon the head when drunk. 



Fractures of the skull. It is not easy to 

 actually fracture the skull of a young infant. The skull 

 as a whole at this age is imperfectly ossified, the sutures 

 are wide, and between the bones there is much 

 cartilage and membrane. Moreover, the bones them- 

 selves in early life are elastic, and comparatively soft 

 and yielding. If a blow be inflicted upon the vault 

 in a young child the most probable effect, so far as 

 the bone itself is concerned, is an indenting or 

 bulging in of that bone unassociated with a fracture 

 in the ordinary sense. In this particular relation, the 

 skull of an infant is to that of an old man as a 



