At operation: Sclerosis of bone, 1 case. Tuberculous mass, 1 case. Subdural cyst or hæmatoma, 8 cases. Scalp adherent to dura, 3 cases. Scar in brain, 1 case. Œdema of brain, 3 cases. Nil found, 1 case. Some lesion, such as might be accepted as responsible for the development of the fits, was discovered in 17 out of 18 cases. Duret’s experience tends to bear out the view that some pathological lesion will be found in almost every case. In 67 cases reported the following conditions were found:-- Depression of bone, 27 cases. Splinters of the internal table, 15 cases. Cysts, subdural, 4 cases. Thickening of membranes, 7 cases. =Operation.= When the localization of the trouble is suggested by the presence of focal symptoms, and by a corresponding scalp- or bone-injury, no difficulty need be experienced in determining the site of exploration. When the fits are associated with definite focal symptoms, but without the supplementary evidence obtained by visible signs of external injury, exploration should be conducted over that region of the brain from which the fits appear to emanate. In the absence of all localizing brain symptoms, operative measures should be carried out over the site of scalp or bone lesion. Whatever the circumstances of the case, the preliminary details are identical. The scalp is shaved, cleansed, the head enveloped in gauze, and the scalp-tourniquet applied. =The formation of the scalp-flap.= When the scalp is adherent to the bone, the incision, carried throughout down to the bone, is made in such a manner that the flap will not only allow of the detachment of the scar, but will also permit of the complete exposure of the neighbouring portion of the skull. When the scalp is adherent to dura or brain, as the result of osseous deficiency, the edge of the knife should be directed towards the under aspect of the flap, and the flap carefully peeled away from the region of the gap. The examination of the bone. _When no fracture is found_, the operator should trephine over the cortical area from which the trouble appears to emanate. _When a fissured fracture is found_, trephining is carried out where the line of fracture cuts across that region of the brain which appears to be involved. _When a depressed fracture is found_, the trephine is applied in such a manner that the circle just includes the outer segment of the depression. After removal of the disk, the dura mater should be peeled away from the under surface of the bone, and the whole of the depressed area cut away with the craniectomy forceps.