re of middle meningeal artery) and serum. The symptoms may come on suddenly or gradually. Wounds of the brain present very great difficulties, and vary greatly in their effect, very slight wounds producing severe symptoms, and vice versâ. A person may receive an injury to the head, recover from the first effects, and then die with all the symptoms of compression from internal hæmorrhage. This is due to the fact that the primary syncope arrests the hæmorrhage, which returns during the subsequent reaction, or on the occurrence of any excitement. Inflammation of the meninges or brain may follow injuries, not only to the brain itself, but to the scalp and [27] adjacent parts, as the orbit and ear. Inflammation does not usually come on at once, but after variable periods.

2. Injuries to the Spinal Cord may be due to concussion, compression (fracture-dislocation), or wounds. That the wound has penetrated the meninges is shown by the escape of cerebro-spinal fluid. The cord and nerves may be injured (1) by the puncture; (2) by extravasation of blood and the formation of a clot; and (3) by subsequent septic inflammation. Division or complete compression of the cord at or above the level of the fourth cervical vertebra is immediately fatal (as happens in judicial hanging). When the injury is below the fourth, the diaphragm continues forcibly in action, but the lungs are imperfectly expanded, and life will not be maintained for more than a day or two. When the injury is in the dorsal region, there is paralysis of the legs and of the sphincters of the bladder and rectum, but power is retained in the arms and the upper intercostal muscles act, the extent of paralysis depending on the level of the lesion. In injuries to the lumbar region the legs may be partly paralysed, and the rectal and bladder sphincters may be involved.

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