=9= _cases detained for 14 to 21 days_ (_probably cerebral contusion_). _Temperature_ on admission: 2 subnormal. 3 normal. 4 slightly raised. _Pulse_ on admission: 6 subnormal. 1 normal. 2 accelerated. =3= _cases detained for 21 to 30 days_ (_certainly cerebral contusion_). _Temperature_ on admission: 1 normal. 2 slightly raised. _Pulse_ on admission: 1 subnormal. 1 normal. 1 accelerated. Still, when all is considered, concussion and compression are but ill-defined from one another, both in their clinical and pathological aspects. The more indefinite cases of concussion are probably such as border on compression, the increasing œdema gradually carrying the patient across the border line between the two conditions. In the present state of our knowledge respecting concussion or cerebral shock it may, I think, be accepted (1) that concussion is dependent on an acute inhibition or paralysis of the vaso-motor centre; (2) that the milder cases are unassociated with any pathological visible changes; (3) that the prolongation and severity of the depression stage are directly proportionate to the extent of the brain lesion, such lesions varying from œdema and contusion to extensive hæmorrhages and lacerations. Its symptomatology. _The stage of depression._ The symptoms are evoked immediately on the receipt of the blow, the patient falling to the ground from lack of muscular control and loss of consciousness. The muscular system is completely relaxed, the limbs, when raised, falling helplessly to the ground. The face is deathly pale, the eyes usually open, fixed, and expressionless, the pupils equal, commonly dilated and responsive to light. The patient _may_ be aroused by strong stimuli--pinching, shouting in the ear, pressure over the supra-orbital nerves, &c. The pulse is small, slightly accelerated, and occasionally intermittent. The respiration is weak, shallow, and often irregular. The temperature is lowered, sometimes to such an extent that it cannot be registered on the thermometer. The surface of the body is cold and clammy, beads of sweat standing out on the brow. The deep reflexes are abolished. Some attempts may be made at swallowing when fluids are placed in the mouth. Urine is often expelled at the time of the accident, and, more rarely, fæces may also be passed involuntarily. The condition either gives place to that of reaction or the state of unconsciousness and collapse becomes more profound, in which case the prognosis is most unfavourable.