juries at first sight apparently
slight may prove fatal from haemorrhage or infection; on the other
hand, recovery has followed injuries of great severity--for example,
the famous "American crowbar case," in which a bar of iron three and a
half feet long and one and a half inches thick passed through the
head, and yet the patient recovered.

It is convenient to consider the injuries of the brain before those of
the skull.

TRAUMATIC LESIONS OF THE BRAIN

It is probable that in all cases of injury to the head in which a
patient loses consciousness, there is some definite damage to the
cerebral tissue. This takes the form of a greater or less degree of
contusion or laceration, and the lesions are usually most severe and
dangerous when the skull is fractured and fragments are driven in upon
the brain, but they may exist--indeed they may be very extensive--in
the absence of fracture.

Several degrees are recognised.

(1) Numerous minute _petechial haemorrhages_ may be found widely
scattered throughout the brain substance, as a result of a diffused
blow on the head, which has shaken up the brain and caused symptoms of
cerebral shock or "concussion." We have found, on microscopic
examination in such cases, in addition to these small extravasations,
collections of colloid bodies, patches of miliary sclerosis, and
chromatolysis and vacuolation of nerve-cells.[3]

[3] Miles, _Laboratory Reports, Royal College of Physicians,
Edinburgh_, vol. iv.

(2) In more severe cases there are often several _visible areas of
extravasation_, most commonly in the grey matter of the cortex (Fig.
184). These foci vary in size from a split-pea to a hazel-nut, and
consist of a dark central zone of extravasated blood, surrounded by an
area of "red softening" of the brain matter, beyond which are numerous
minute capillary haemorrhages. These intra-cerebral lesions may be
accompanied by an effusion of blood into the meshes of the
arachno-pial membrane, and they may occur either at the part of the
head struck, or at the opposite pole of the axis of percussion--the
so-called point of _contre-coup_. The symptoms vary with the size and
site of the extravasations. It is probable that the phenomena of
"cerebral irritation" are to be explained by the occurrence of such
haemorrhages widely scattered through the cerebral cortex. Effusions
into the cortical motor areas give rise to irritation or paralysis of
the muscles governed by the affected cent