chap, ii.] BONY VAULT OF THE CRANIUM. 25 



this bone. It must receive, however, much protection 

 from its connections with the two parietal and tem- 

 poral bones, and from its articulation with the elastic 

 vertebral column. 



Fractures of the base of the skull may be 

 due to (1) direct or to (2) indirect violence, and, most 

 commonly of all, to (3) extension of a fracture from 

 the vault. (1) The base has been fractured by direct 

 violence by foreign bodies thrust through the nasal 

 roof, through the orbital roof, and through the base as 

 it presents in the pharynx. The posterior fossa can 

 also be fractured by violence applied to the nape of the 

 neck. (2) Of fractures by indirect violence the following 

 examples may be given : Blows applied to the lower 

 part of the frontal bone have been associated with no 

 lesion other than a fracture of the cribriform plate or 

 of the orbital part of the frontal, these parts being 

 much disposed to fracture on account of their extreme 

 tenuity. In falls upon the chin, the condyle of the 

 lower jaw has been so violently driven against the 

 glenoid cavity as to fracture the middle fossa of the 

 skull. Chassaignac gives a case where the condyle 

 was actually thrust into the cranial cavity, and 

 produced an abscess in the superimposed part of the 

 brain. When the body in falling has alighted upon 

 the feet, knees, or buttocks, the force has been trans- 

 mitted along the vertebral column, and has led to 

 fracture of the base in the occipital region. Such 

 accidents are most apt to occur when the spine is kept 

 rigid by muscular action, and the mechanism involved 

 is precisely similar to that whereby the head of a 

 broom is driven more firmly on to the broom-handle 

 by striking the extreme end of the stick against the 

 ground. The theory that the base is often broken by 

 contre-coup is pretty generally abandoned, although 

 there are a few cases that appear to support the 

 suggestion. Such a case was recorded by Mr. 



