ssion
are usually most prominent at first, and those of compression only
ensue after a varying interval, during which the patient as a rule
regains consciousness. In some cases, indeed, he is able to continue
his work, or to walk home or to hospital, before any evidence of
intra-cranial mischief manifests itself. This "lucid interval" helps
to distinguish the symptoms due to middle meningeal haemorrhage from
those of laceration of the brain substance, as in the latter the
symptoms of concussion merge directly into those of compression.
Lumbar puncture may aid in the differential diagnosis between
extra-and intra-dural haemorrhage, as blood is present in the fluid
withdrawn in the latter, but not in the former.

A few hours after the accident the patient experiences severe pain in
the head, and he usually vomits repeatedly. For a time he is restless
and noisy, but gradually becomes drowsy, and the stupor increases
more or less rapidly until coma supervenes. The pulse usually becomes
slow and full. The respiration is rapid (30 to 50), and becomes
greatly embarrassed and stertorous. The temperature progressively
rises, and before death may reach 106 deg. F., or even higher. Monoplegia,
usually beginning in the face or arm on the side opposite to the
lesion, gradually comes on, and is followed by hemiplegia, from
pressure on the motor areas, underlying the clot. The condition of the
pupils is so variable as to have no diagnostic value; but if both are
widely dilated and irresponsive to light, the prognosis is grave.
Death usually ensues in from twenty-four to forty-eight hours, unless
the pressure within the skull is relieved by operation; even after
removal of the clot death may ensue if the brain has been lacerated,
or if there is haemorrhage at the base.

When the haemorrhage takes place from the anterior branch, the clot
tends to spread towards the base, and may press upon the cavernous
sinus, causing congestion and protrusion of the eye, with paralysis of
the oculo-motor nerve and wide dilatation of the pupil.

In some cases of middle meningeal haemorrhage there is no gross injury
to the brain; the area underlying the clot is merely compressed and
emptied of blood, and, on being exposed, the brain is found flattened,
or even deeply indented by the blood-clot, and it does not pulsate. If
the clot is removed, the brain may regain its normal contour and its
pulsation return. The mortality is over 50 per cent.

If the