o inducing a fall in the blood pressure and a profound anaemia of
the brain. The disturbance of the cerebro-spinal fluid may at the same
time produce the microscopic lesions in the brain tissues described on
p. 341.

The symptoms of shock may be the only evidence of injury, or they may
be superadded to those of fracture of the skull, or laceration of the
brain.

The _clinical features_ vary according to the severity of the
violence. In the slightest cases the patient does not lose
consciousness, but merely feels giddy, faint, and dazed for a few
seconds. His mind is confused, but he rapidly recovers, and, perhaps
after vomiting, feels quite well again, save for a slight shakiness in
his limbs.

In more severe cases, immediately on receiving the blow the patient
falls to the ground unconscious. Sometimes he suffers from a general
tetanic seizure associated with arrest of respiration, which is
usually of short duration and is frequently overlooked, but may prove
fatal. The pulse is slow, small, and feeble, and is sometimes
irregular in force and frequency. The respirations are short, shallow,
slow, and frequently sighing in character. The temperature falls to
97 deg. F., or even lower. The skin is cold and pallid and covered with
clammy sweat, and the features are pinched and pale.

In uncomplicated cases the pupils are usually equal, moderately
dilated, and react sluggishly to light. The patient can be partially
roused by shouting or by other forms of external stimulation, but he
soon subsides again into a lethargic condition. Although voluntary
movement and the deep reflexes are abolished, there is no true
muscular paralysis.

After a period, varying from a few minutes to several hours, he
rallies, the first evidence often being vomiting, which is usually
repeated. Sometimes reaction is ushered in by a mild epileptiform
seizure. He then turns on his side, the face becomes flushed, and
gradually the symptoms pass off and consciousness returns. The
temperature rises to 99 deg. or 100 deg. F., and in some cases remains
elevated for a few days. In most cases it falls again to 97 deg. or 97.5 deg.,
and remains persistently subnormal for one or two weeks. During
reaction the pulse becomes quick and bounding, but after a few hours
it again becomes slow, and usually remains abnormally slow (40 to 60)
for ten or fourteen days. There is sometimes a tendency to
constipation, and for the bladder to become distended, although