=Fissured fractures.= If, after thorough exposure of the parts, the operator is satisfied that he has to deal with an uncomplicated fissured fracture, the scalp-flap is accurately sewn into position (see p. 16). On the other hand, if the symptoms point to the presence of an extra-dural hæmorrhage, the bone is trephined where the fracture crosses the line of the suspected vessel and the conditions treated as described under middle meningeal hæmorrhage. In subdural extravasation the trephine is applied over that part of the brain, in the immediate vicinity of the fracture, from which the symptoms appear to emanate, and the conditions treated as described under subdural hæmorrhage. In a certain proportion of cases the symptoms point to a marked increase of intracranial pressure without definite localizing features, a condition pointing to diffuse subdural hæmorrhage, with or without brain laceration. Under such circumstances much may be done to relieve the increased intracranial pressure by carrying out the operation of ‘cerebral decompression’ (see p. 121). =Depressed fractures.= The operative details vary according to the nature of the osseous lesion:-- (_a_) If the depressed fragments of bone are so interlocked that elevation is impossible (e. g. pond and gutter fractures), it will be necessary to trephine in the immediate vicinity of the depression, in order to lessen the mutual attachment of the fragments one to another, so obtaining sufficient purchase for their elevation or removal. The pericranium is stripped away from the region of the depression (see Fig. 49), and a small trephine applied in such a manner that the trephine circle includes the outer part of the depressed area. Care must be taken to avoid more pressure over the depressed fragments than is absolutely necessary, for fear of causing further damage to the underlying structures. This advice is all the more important when it is realized that the fracture of the internal table is almost invariably more extensive than that which involves the visible external table of the skull.