the inner table is more widely shattered at the
aperture of entrance, and the outer table at the aperture of exit. Von
Bergmann reported thirty cases in which the inner table alone was
fractured by a blow on the head.

Fractures by _indirect_ violence--that is, fractures in which the bone
breaks at a point other than the seat of impact--are almost always due
to violence inflicted with a blunt object, and acting over a wide
area--such, for example, as when the head strikes the pavement. Much
discussion has taken place as to the method of their production. It
has been shown that when the skull is depressed at one point by a
force impinging on it, it bulges at another, so that its whole contour
is altered. But the elasticity of the bone varies at different parts
of the skull, owing to differences in thickness and in structure. If,
therefore, the part which is depressed--that is, the part directly
struck--happens to be less elastic than the part which bulges, it
gives way, and a fracture by "bending" results; but if the bulging
part is the less elastic, it bursts outwards--_fracture by_
"_bursting_." The term "fracture by _contre-coup_" has been
incorrectly applied to such fractures when the area of bulging happens
to be opposite to the seat of impact. _Contre-coup_, properly
so-called, is only possible in a perfectly spherical body, which, of
course, the skull is not.

When a high-velocity bullet penetrates the head, it exerts on the
incompressible, semi-fluid brain an explosive (hydro-dynamic) force,
which is transmitted to all points on the inner surface of the skull
and leads to shattering of the bone.

_Repair._--The repair of fractures of the skull is usually attended
with an exceedingly small amount of callus. Except in the presence of
infection, separated fragments live and become reunited, but they may
unite in such a manner as to project towards the brain and, by
irritating the cortical centres, cause traumatic epilepsy. In
comminuted fractures, the lines of fracture remain permanently visible
on the bone, but fissured fractures may leave no trace. Gaps left in
the skull by injury or operation are, after a time, filled in by a
fibrous membrane, which may undergo ossification from the periphery
towards the centre, but unless the aperture is a small one it is
seldom completely closed by bone. The new bone which forms is derived
from the old bone at the margins of the opening. Permanent defects in
the skull are