CHAPTER XIII

INJURIES OF THE SKULL

Contusions--FRACTURES--Of the vault: _Varieties_--Of the Base:
_Anterior fossa_--_Middle fossa_--_Posterior fossa_.

The bones of the skull may be contused or fractured. These injuries
are not in themselves serious: their clinical importance is derived
from the injury to the intra-cranial contents with which they are
liable to be associated.

#Contusion# of the skull may result from a fall, a blow, or a gun-shot
injury. In the majority of cases the damage to soft parts--scalp,
meningeal vessels, or brain--overshadows the osseous lesion, which of
itself is comparatively unimportant.

FRACTURES OF THE SKULL

While it is convenient to consider separately fractures of the vault
and fractures of the base of the skull, it is to be borne in mind that
it is not uncommon for a fracture to involve both the vault and the
base. Fractures in either situation may be simple or compound.

FRACTURES OF THE VAULT

#Mechanism.#--When the skull is broken by _direct_ violence, the
fracture takes place at the seat of impact, and its extent varies with
the nature of the impinging object and the degree of violence exerted.
If, for example, a pointed instrument, such as a bayonet, a foil, or a
spike, is forcibly driven against the skull, the weapon simply crashes
through the bone, disintegrating it at the point of entrance, and
cracking or splintering it for a variable, but limited, distance
beyond. On the other hand, when the head is struck by a "blunt"
object--for example, a batten falling from a height--the force is
applied over a wider area and the elastic skull bends before it. If
the limits of its elasticity are not exceeded, the bone recoils into
its normal position when the force ceases to act; but if the bone is
bent beyond the point from which it can recoil, a fracture takes
place--"_fracture by bending_." The bone gives way over a wide area,
the affected portion may be comminuted, and one or more of the
fragments may remain depressed below the level of the rest of
the skull. Cracks and fissures spread widely in different
directions--often (70 to 75 per cent.) extending into the base. In
almost all fractures of the vault the inner table splinters over a
wider area than the outer, partly because it is more brittle and is
not supported from within, but also because the diffusion of the force
as it passes inwards affects a wider area. If a bullet traverses the
cranial cavity