trephine. The bone dust is dry until the diploë is reached; it is then soft and bloody. It is a good plan while trephining any part of the skull to imagine that it is the thinnest skull in existence and that it is of variable thickness at different parts of the groove. This will tend to make one proceed cautiously. At frequent intervals the depth. of the groove should be measured by inserting into it the eye end of a needle held by a pair of pressure forceps. A slight feeling of irregularity will be detected as the needle is carried around the groove; if the inner table has been perforated, the needle will catch slightly instead of moving smoothly. All bone dust is immediately wiped away. As one side of the groove reaches the inner table great caution is needed that in completing the section the dura is not injured. The trephine is tipped slightly towards the uncut portion; greater pressure is put upon this side as the cut is made. Then the button of bone is removed entire. If the button is not easily removed, no attempt to remove it should be made by tipping the trephine and prying it out. A narrow elevator will often remove it in whole or in part, and then the rongeur forceps will complete its removal and smooth the edge of the opening. If the opening made is insufficient it is enlarged by the rongeur forceps. If the hemorrhage is from the meningeal artery the clot is evacuated, the vessel secured by fine silk ligature or a suture of fine silk is passed with a small curved needle through the dura and around the vessel and tied. The bone removed is not to be replaced. Drainage of the wound should be based upon the same principles as drainage elsewhere. Bleeding from the bone will often cease spontaneously after a few moments; if not the bone may be crushed about the bleeding vessel or a plug of sterile wood or Horsley's wax plug may be used. If there is much oozing of blood or serum or cerebrospinal fluid, and if infection is suspected, drainage is to be em ployed. Under other conditions it is not to be used. The wound is best drained by a small, soft rubber tube. The wound in the scalp is closed in whole or in part by sutures of silkworm gut. If the dura is to be opened, it is incised by the knife and divided by a small pair of blunt-pointed scissors, avoiding so far as possible all vessels. The dura should be divided a quarter of an inch from the bony opening to permit of subsequent suturing, if that is deemed necessary. The after-care of the operation of trephining. — In uncomplicated cases the patient is kept in a darkened room and as quiet as possible for three or four days. A cold water bag or coil is kept constantly on the head. Calomel in divided doses ( gr. each hour for ten doses) is given by mouth. The diet is for the first few days a liquid one. After a week or a week and a half the patient is allowed to be up. In cases complicated by probable intracranial lesions the patient must be kept quiet a longer time. The wound is cared for according to ordinary surgical principles. If a drain has been used, it must be proved to be efficient. If provisional sutures have been placed, these are tied upon removal of the drain. Hernia cerebri is the term applied to a protrusion of the brain through the opening left after trephining. This occurs when there is abnormal intracranial pressure. The whole mass of the hernia is not ordinarily brain tissue, but is largely made up of granulation tissue- fungous granulations. It is a most distressing condition which may complicate especially septic cases. Cleanliness, compresses of alcohol and support to the part are indicated. Concerning the closure of bony defects of the skull, how harmful such defects are, whether pedunculated flaps of periosteum shall be used to close them, or gold foil or rubber tissue or egg membrane or celluloid disks, these questions are still open for discussion. The value of the Gigli saw is undoubted, and its use in forming osteoplastic flaps for exploratory purposes is of extreme interest, but this does not concern us in this discussion. The electric motors used to drive a saw or trephine are not likely to come into general use. |