Sometimes the abscess under the bone is of a chronic nature, as in the following case:—The patient, a boy, æt. 11, received a blow on the vertex, after which a puffy tumour formed in the injured scalp, and was freely incised. He afterwards became subject to epileptic fits, which were relieved by copious evacuation of matter from the wound. Exfoliation of the cranium occurred; one small sequestrum was separated, which involved the whole thickness of the bone, and a collection of matter between the dura mater and skull-cap was thereby exposed. The contained matter was evacuated, and the wound was carefully dressed, with the view of procuring adhesion between the membrane and bone, but without effect. The dura mater was ascertained to be extensively detached around the opening; it was found necessary to remove a large portion of bone by means of the trephine and cutting pliers, and then the dura mater soon became united with the integuments of the head. Many months afterwards, the patient complained of severe pain in the back of the neck; an abscess formed in that situation, and, pointing under the right scapula, was opened. Weakness of the right arm and of the inferior extremity suddenly supervened, and the patient gradually sunk. On examination after death, the cervical portion of the spinal chord was found much softened, with infiltration of purulent matter into its substance. The deficiency in the cranium was supplied by a ligamentous expansion, to which the dura mater and scalp adhered intimately.