HEAD 253 (3) Bleeding, or discharge of cerebro-spinal fluid from the nose, mouth, or one or both ears. (4) Lesions of the nerves issuing from the base of the skull giving rise to paralysis or loss of sensation of the parts supplied by them. The result is not always fatal. Sometimes recovery takes place, through headache, deafness, or other nervous derangements may persist for a long time. Contusions and Lacerations of the Brain.—These injuries are caused by the application of violence to the head and may occur with or without external injury to the scalp and fracture of the skull. They are seen super- ficially on the surface of the brain or deep within its substance, and are associated with punctate haemorrhages1 limited in small areas or multiple haemorrhages diffused largely within the brain tissues. These injuries are commonly found under the site of application of the blow, but they are sometimes found on the surface of the brain diagonally opposite to the site of impact, and are called contre-coiip injuries. They are most commonly found on the undersurfaces of the frontal lobes and near the tips of the temporal and frontal poles. Contre-coup lesions of the brain were once thought to be caused by the brain moving within the skull in a straight line with the force of the blow and striking against its opposite side, but from experiments on mechanics of head injuries Holbourn 5 has demonstrated that contre-coup lesions are chiefly due to local distortion of the skull and sudden rotation of the head as a result of a blow, which arouse shear strains produced by the pulling apart of the constituent particles of the brain. Shear strains occur in all parts of the brain, but they occur to a large extent at the base of the frontal lobe and the tip of the temporal lobe, as the skull gets a good grip on the brain in this region owing to the projecting ridge of the sphenoid bone. Hence severe and extensive injuries occur in this region when a blow is struck on the occiput. On the other hand, contre-coup injuries which are caused by rotation will not occur, if the head is so well fixed that it cannot rotate at all when it receives a blow. Concussion of the Brain.—This is a rotational injury, as it will occur only when the head is free to move but not when it is fixed. It is popularly known as " stunning", and may be produced by direct violence on the vertex, by a violent fall upon the feet or nates from a height, or by an unexpected fall on the ground, when pushed forcibly by a running cart or even by a bicycle. Symptoms.—The symptoms depend upon the nature of the injury. Thus, the patient may become dazed and giddy with or without falling, if there is slight injury, and recovers in a short time, but he may remain mentally confused for some time and will vomit once or twice. With severe injury the patient falls down and becomes unconscious, though he can often be partially roused by shouting. The muscles are relaxed and flaccid, but there is no paralysis. The sphincters are relaxed with involuntary passage of urine and faeces. The face is pale, and the pupils are equal and usually contracted reacting to light but, in more severe cases, are dilated and insensible to light. The skin is cold and clammy with subnormal temperature. The pulse is rapid, weak, small and hardly perceptible. The respirations are slow, irregular and sighing. Death occurs rapidly from syncope, or recovery follows, with the setting* in of nausea or vomiting. The skin becomes hot and dry, the pulse is full and strong, and the respirations are increased in rate. After apparent recovery 5. Lancet, Vol. II, 1943, p. 438.