2. The escape of cerebro-spinal fluid is of infrequent occurrence, probably due to the fact that the apertures of entry and exit are blocked up with scalp, fragments of bone, and pulped and swollen brain. 3. Concussion and irritation are prominent symptoms, compression is rarely seen in its typical form. As Spencer[60] says, ‘The dominant feature is usually concussion. The extent of the paralysis depends on the region injured, and there is often at first extensive temporary paralysis from vibratory concussion of the brain substance suspending its functions over a wide area around the bullet-track.’ Cerebral irritation and Jacksonian fits are frequently observed. =Indications for operation.= There is a great uniformity of opinion with regard to the indications for operation as expressed by those who have had considerable experience in wounds of this nature. One has only to glance through the works of recognized authorities--Spencer,[61] Bowlby,[62] Makins,[63] Lawford Knaggs,[64] &c.--to see that it is an accepted rule that all bullet-wounds of the skull and brain call for early operative interference, it being granted that the condition of the patient is compatible with such treatment. =Operation.= The operative details may be considered under two headings:-- (_a_) The exploration of the wounds of entry and exit. (_b_) The search for and removal of the bullet. [Illustration: FIG. 88. TO ILLUSTRATE THE EFFECTS PRODUCED BY A PERFORATING BULLET-WOUND. 1, The inverted scalp at wound of entry; 2, Subaponeurotic hæmorrhage; 3, The wound of entry into the skull; 4, Extra-dural hæmorrhage; 5, Lacerated dura mater; 6, Subdural hæmorrhage; 7, In-driven fragments of bone; 8, The passage through the brain-substance; 9, Ventricular hæmorrhage; 10, The wound of exit through the brain; 11, Subdural hæmorrhage; 12, The wound of exit through the dura mater; 13, The wound of exit through the skull; 14, The wound of exit through the scalp.] _The exploration of the wounds of entry and exit._ Whether the skull be penetrated or perforated, the wounds are investigated after similar general principles. After careful shaving and cleansing of the whole scalp, and after application of the scalp-tourniquet, a scalp-flap is turned down, the centre corresponding as far as possible to the site of entrance or emergence of the bullet. The under aspect of the flap is examined for loose fragments of bone, hair, portions of headgear, &c. These are removed and the flap cleansed. The bone is next examined. All loose fragments are removed, both large and small. The smaller are discarded, the larger are boiled (for ten minutes) and preserved in hot saline solution for replacement at the termination of the operation, if such a course should be deemed advisable (see p. 132). Those fragments of bone which retain their pericranial attachments are merely elevated and turned aside, to be again placed in position at the proper time.