=General effects.= As soon as the clot becomes of sufficient size as to exert general pressure on the brain, symptoms of compression become evident, the patient first entering on the stage of ‘slow cerebration’. He is dull and apathetic, showing marked delay in responding to questions. As the pressure increases, he gradually passes into a state of unconsciousness. The pulse becomes full and slow, the blood-pressure rises progressively (to 200 or more mms. of Hg.), respiration is laboured and stertorous, and the temperature raised (rising progressively). The skin is hot, the face turgid and cyanosed. If the pressure is unrelieved, stimulation of the medullary centres gives place to exhaustion, the pulse becoming irregular and rapid, blood-pressure falls rapidly, and respiration is of irregular rhythm and finally Cheyne-Stokes in character. Finally, the patient becomes completely comatose, the pupils are widely dilated, and the cornea insensitive. Both urine and fæces may be passed (through paralysis of the sphincters), the extremities exhibit flaccid paralysis and the reflexes are abolished. Death occurs primarily through paralysis of the respiratory centre. =Local effects.= In many cases considerable help to diagnosis may be obtained by external examination--bruising and ecchymosis, or definite hæmatomata, in the temporal or parietal regions. In some cases the hæmatoma may pulsate, and in others the application of pressure to the hæmatoma will lead to the development of fits involving the face and extremities on the contra-lateral side. Copious hæmorrhage from the ear should always arouse suspicion as to the probability of an extra-dural hæmorrhage (see p. 97). The _anterior_ branch of the artery, as it passes upwards towards the vertex, overlies the pre-Rolandic or motor area. The pressure exercised on that region of the brain leads--according to the site of extravasation and the degree of pressure exercised--to the development of twitchings, convulsions, spasticity, or paralysis of the muscles of the face, upper and lower extremities on the contra-lateral side of the body. [Illustration: FIG. 51. TO ILLUSTRATE COMPRESSION OF THE BRAIN. As produced by an extra-dural hæmorrhage from the posterior branch of the middle meningeal artery.] The late Professor von Bergmann[26] pointed out that the arm area is most commonly affected, and that the leg area is never alone implicated. Wiesmann[27] states ‘that isolated paralysis of the leg area is never seen, but only paresis when the arm is paralysed, or both may be similarly affected at once; convulsions may precede the affection’.