106 CLINICAL APPLIED ANATOMY. 



direct violence. The bone which is depressed may he the whole 

 thickness of the vault that is, the outer table, the diploe and the 

 inner table and this condition is the commonest. On the other 

 hand the external table alone may be driven in without the 

 internal table being in any way depressed. This occurs most 

 usually and typically where the two tables are separated from one 

 another, not by diploe, but by an air space, as for instance in the 

 region of the frontal sinus. 



It is doubtful whether depression of the internal table alone 

 ever occurs. 



In quite young subjects, owing to the elasticity of the bones 

 entering into the formation of the vault, it is possible for depres- 

 sion to occur without an actual fracture, and in some cases the 

 depressed bone may become spontaneously restored to its normal 

 position. 



In depression of both tables it is usual for the internal to be 

 depressed over a wider area than the external, which is due to the 

 radiation of the force from the point at which it is applied, and 

 the curvature of the bone entering into the formation of the skull. 



In the diagnosis it is important to distinguish depressed frac- 

 tures from natural depressions about the skull. Perhaps the most 

 likely spot at which a mistake may arise is in the anterior part of 

 the temporal region, where the upper border of the zygoma, the 

 external angular process of the frontal bone and the commence- 

 ment of the temporal ridge together form a raised margin, which, 

 if associated with the history of a blow and the presence of a 

 haematoma of the scalp, very closely simulates a depressed frac- 

 ture. A conclusive diagnosis however can easily be made by 

 comparing the sound with the injured side, the former exhibiting 

 the pseudo-depression even more markedly than the latter. Other 

 natural depressions sometimes mistaken for depressed fractures 

 are found about the occipital region in connection with the spaces 

 between the nuchal lines. 



An elevated fracture is usually seen at the aperture of exit of 

 a bullet, and is therefore commonly an open fracture, the scalp 

 as well as the bone having been traversed by the missile. In this 



