In simple fractures the diagnosis is frequently obscured by an extensive subaponeurotic or subpericranial hæmatoma. Irregularities of surface are more or less diagnostic of a solution in the surface of the bone, and a linear hæmatoma is of corresponding clinical value. In any case, the presence of an extensive hæmatoma must be regarded as of so suggestive a nature that exploration is called for, more especially when prolonged concussion or compression are co-existent. Such treatment is imperative when the hæmatoma--whether diffuse, localized, or linear--pulsates, such a condition implying a breach in the surface of both bone and dura with communication between the extra-cranial and some intra-cranial hæmorrhage. Pringle[24] lays stress on the value of percussion as an aid to diagnosis. ‘The patient’s head must be supported beneath the occiput, the mouth either open or shut--it matters not, so long as it is the same throughout the examination--and the skull is struck sharply with the finger. When a fracture is present, two changes in note may be elicited. Either a note lowered in pitch over the fracture zone, or, in addition, a definite crack-pot sound. The note elicited is most typical when comminution is present, and some fragments loose. A fracture of a T or L or V-shape gives the best crack-pot sound, and the crack quality is always most pronounced when the percussing finger comes over the angular portion of the bone. Hæmorrhage into the subaponeurotic region blurs the note.’ [Illustration: FIG. 42. A COMMINUTED FRACTURE OF THE SKULL.] If time and occasion permit, an X-ray photograph will clinch the matter. When the fracture involves the internal table alone, the symptoms are less definite. Teevan stated that this class of fracture does not lead to the development of any symptoms unless:-- The middle meningeal artery be injured. The dura mater and brain be irritated. The brain be compressed. He also adds that the existence of the following features suggests the nature of the injury:-- The history of a slight blow, probably with a small body. The blow situated over the parietal region. [Illustration: A B FIG. 43. AN EXPLOSIVE FRACTURE OF THE VAULT OF THE SKULL. A shows the right side of the skull and the site of entry of the bullet. B shows the extension of the fracture round the left half of the skull. In the left upper parietal region (Fig. B) a fissured fracture is seen where the bullet failed to perforate the skull.] Chronic fixed pain, some days or weeks afterwards, with symptoms of brain-irritation or encephalitis, and even suppuration, suggesting irritation of the meninges and brain by spicules of bone. Compression and paralysis on the opposite side of the body some hours afterwards, as the result of injury to the middle meningeal artery. Symptoms of compression early and slight, combined with partial paralysis of the opposite side of the body.