406 Anatomy Applied to Medicine and Surgery. 



the exterior, into the sinuses in the interior of the skull. 

 This secondary cerebral involvement may occasionally be 

 seen in such conditions as erysipelas of the face or head, 

 septic wounds of the scalp, osteomyelitis, etc. 



Fractures of the skull are of importance, chiefly in 

 so far as they affect the contents of the cranium, and, in 

 connection with fractures, it is of interest to note some 

 of the means provided for the protection of the brain from 

 injury, and, among these, are the following: (1) The mo- 

 bility of the scalp which tends to convert a direct into a 

 glancing blow; (2) the dome-like shape of the skull and 

 the mobility of the head on the spine; (3) instead of one 

 uniform bone forming the skull, its division into a num- 

 ber of individual bones, separated, excepting in later life, 

 by the sutural membrane, tends to diffuse the vibrations 

 which might otherwise produce a fracture; (4) the elas- 

 ticity of the outer table and the power of deadening the 

 vibrations possessed by the cancellous diploe; (5) the 

 pericranium without and the dura mater within, which 

 act, just as a wet washleather covering and lining would 

 to a bell, viz. , dampen its vibrations (Nancrede) ; 

 (6) the arrangement, at some of the sutures, whereby a 

 part of the border of one bone overlaps that of another, as 

 at the upper part of the frontal bone, or on the lower part 

 of the parietal, or where the squamous portion overlaps 

 the inferior border of the parietal. The part this arrange- 

 ment plays in protecting the brain beneath is shown by 

 the diffusion of the effects of a blow, received on the skull, 

 to distant parts rather than its concentration upon the tis- 

 sues directly beneath, and this diffusion is seen in in- 

 stances where pain is felt in the cheek, the result of a blow 

 received on either the upper part of the frontal or parietal 

 bones. In the case of the latter, the upper part of the 

 parietal being depressed by the blow, would force the lower 



