d. Beyond this
extensive haemorrhages at the base of the skull were common.

With regard to the extensive character of the brain destruction in the
region of the aperture of exit, it must be borne in mind that this
lesion corresponds in position with one which would exist even if the
injury were of a non-penetrating degree. A large proportion of the
contusion and destruction is therefore explained by violent impact of
the projected brain with the skull prior to the passage of the bullet,
and not to the direct action of the bullet on the tissues.

These cases of 'general injury' afford a marked example of the lesions
to which the term 'explosive' has been applied, and as such have an
important bearing on the theories held as to the mode of production of
explosive effect. The increased area of tissue damage at the aperture of
exit favours the theory of direct transmission of a part of the force
with which the bullet is endowed, to the molecules of tissue bounding
the track made by the projectile. Thus the area of destruction
corresponds with the cone-like figure which one would expect to be built
up by the vibrations spreading from the primary point of impact. The
exit region of the skull is subjected not alone to the force of the
travelling bullet, but also to that exerted over a much wider area by
the tissue to which secondary vibrations have been communicated. The
brain itself is, in fact, dashed with such violence against the bone as
to cause a great part of the injury.

No doubt the brain in its reaction to the bullet forms as near an
approach to a fluid as any solid tissue in the human body, and
experimental observation has shown how greatly its presence or absence
in the skull affects the degree of comminution on the exit side; hence
the fondness for the so-called hydraulic theory that has been always
exhibited in the case of these injuries. The localisation of the injury
in its highest degree to the neighbourhood of the exit aperture,
however, shows that in any case the main wave takes a definite direction
in a course corresponding to that of the bullet.

The real importance of the presence of the brain within the skull in
increasing the amount of damage at the exit end of the track, is as a
medium for the ready transmission of forcible vibrations. That the
latter are to some extent conveyed as by a fluid is evidenced by the
occasional presence of brain matter and fragments of bone in the
aperture of entry, wh