FISSURED FRACTURES.—These fract ures are caused by the "binding" or "bursting" of the skull under pressure applied broadly. They are the "indi rect" fractures of the skull, just as the circumscribed fractures are "direct." Consequently fissured fractures are much more common in the base, and circum scribed fractures more common in the vault. The bursting force may make itself felt in a radial direction or in a direction at right angles to this, and the fissures are therefore usually dispersed in one of these two directions, although the irregular thickness and elasticity of the skull, especially its base, is liable to impart to the fissure a ziz-zag course. The fissure may occur only at some point quite distant from the point of impact and is there often termed a contrecoup, a misleading term, for there is no contre coup. On the other hand, the fissure may be so extensive as to allow the two halves of the skull to be freely movable upon each other. Since the cause of those fractures is generally a blunt in strument, they are less often com pounded than the circumscribed fract ures.
These fissures being due to a bursting of the skull on account of a sudden change of shape of the whole globe, it is readily understood that the associated lacerations of and hmemorrhage into the contained structures are likely to be very extensive and to prove rapidly fatal, not in any sense on account of the fracture, but on acount of the trauma that caused the fracture.
DIAGNOSIS.—Fissures in the vault are often compounded and thus readily diag nosed. Care must be taken not to mis take a lacerated aponeurosis for a fissure of the skull. In fissures of the base, however, the diagnosis can rarely be made except by inference. As these fis sures often involve the petrous portion of the temporal bone, rupturing the tym panum, from the ear, mouth, or nose is a fairly-accurate diag nostic sign of fracture of the base. The diagnosis is, however, of very little im portance.