#Fracture of the middle fossa# is usually the result of severe violence applied to the vault, as, for example, when a man falls from a height, or is thrown from a horse and lands on his head. _Clinical features._--The most conclusive sign of fracture of the middle fossa is the escape of dark-coloured blood in a steady stream from the ear, followed by oozing of cerebro-spinal fluid. The bleeding from the ear may go on for days, the blood gradually becoming lighter in colour from admixture with cerebro-spinal fluid. Finally the blood ceases, but the clear fluid continues to drain away, sometimes for weeks, and in such quantity as to soak the dressings and the pillow. In our experience, the escape of cerebro-spinal fluid is much less common than is generally supposed. In most cases, on examining the ear with a speculum, the tympanic membrane is found to be ruptured; when it is intact, the blood and cerebro-spinal fluid may pass down the Eustachian tube into the pharynx. The escape of brain matter from the ear is exceedingly rare. Emphysema of the scalp sometimes results when the fracture passes through the mastoid cells. The facial and acoustic nerves and the maxillary and mandibular divisions of the trigeminal are frequently implicated. Deafness is a serious and not uncommon accompaniment of fracture of the middle fossa, as the fracture involves the labyrinth and is attended with hæmorrhage and the formation of new bone. _Diagnosis._--Care must be taken not to mistake blood which has passed into the ear from a scalp wound, or which has its origin in a fracture of the wall of the external auditory meatus or a laceration of the tympanic membrane, for blood escaping from a fracture of the base. Under these conditions the blood is usually bright red, is not accompanied by cerebro-spinal fluid, and the flow soon stops. It is on record[4] that blood and cerebro-spinal fluid may escape along the sheath of the acoustic nerve without the bone being broken. [4] Miles, _Edinburgh Medical Journal_, 1895. #Fracture of the posterior fossa# is produced by the same forms of violence as cause fracture of the middle fossa; it is specially liable to result if the patient falls on the feet or buttocks. _Clinical Features._--Sometimes a comparatively limited fracture of the occipital bone results, and in the course of a few days blood infiltrates the scalp in the region of the occiput and mastoid, or may pass down in the deeper planes of the neck. As a rule, however, there is no immediate external evidence of fracture. The patient is generally unconscious, and shows signs of injury to the pons and medulla, causing interference with respiration, which soon proves fatal. The rapidly fatal issue of these cases usually prevents the manifestation of any injury to the posterior cranial nerves.