=The operation.= The hair is shaved over the temporal region, with a wide margin to the field of operation. In other respects, those preliminary details should be adopted which are enumerated in Chapter II. The skin incision commences well above and behind the external angular frontal process, is directed along the line of, but below the temporal crest, and curves downwards to terminate just anterior to the tragus of the ear. Pressure is applied during the formation of the incision so as to control bleeding from temporal arteries. The flap, comprising skin, subcutaneous tissue, and superficial temporal artery, is turned down to a zygomatic base, care being taken to avoid injury to the temporal vessels at the base of the flap. The temporal fascia is then incised, parallel to but immediately below the line of the skin incision, and the fascia also turned down towards the zygoma. The temporal muscle is split in the direction of its fibres, from the temporal crest above to the zygoma below, stripped away from the bone and well retracted in both forward and backward directions. In this procedure care must be taken to avoid detachment of the muscle-fibres from the temporal crest. The area of bone exposed, however, should be as extensive as circumstances permit. [Illustration: FIG. 45. INTERMUSCULO-TEMPORAL CEREBRAL DECOMPRESSION. _First stage._ The scalp and temporal fascia have been turned down as separate flaps. The temporal muscle is divided in the direction of its fibres, and the exposed bone trephined.] [Illustration: FIG. 46. INTERMUSCULO-TEMPORAL CEREBRAL DECOMPRESSION. _Second Stage._ The temporal muscle is retracted on either side, the bone has been freely cut away, and the bulging dura mater crucially incised.] [Illustration: FIG. 47. INTERMUSCULO-TEMPORAL CEREBRAL DECOMPRESSION. _Third Stage._ The dural flaps are turned aside, exposing the lacerated temporo-sphenoidal lobe. A rubber drainage-tube has been inserted beneath the lacerated brain, lying on the floor of the middle fossa of the skull and brought to the surface through the scalp-flap.] [Illustration: FIG. 48. INTERMUSCULO-TEMPORAL CEREBRAL DECOMPRESSION. _Fourth Stage._ The temporal muscle-fibres have been approximated, and the temporal fascia reunited in part. The drainage tube is seen to emerge through fascia and scalp.]