_Direction, &c., of _Probable resultant basic fracture._ the applied force._
1. Force applied to The fracture passes backwards from the the median frontal perpendicular plate of the frontal bone to the region. cribriform plate of the ethmoid, thence between the optic foramina to the body of the sphenoid, the thin sinus roof being usually comminuted. From there the fracture diverges to the opposite side, and tearing off the posterior clinoid process, passes along the petro-occipital suture to the jugular foramen, being then continued on the other side of that foramen along the masto-occipital suture, and so again to the vault.
[Illustration: FIG. 32. DIAGRAM OF LINES PURSUED BY BASIC FRACTURES. Force applied to the median frontal region.]
2. Force applied to The fracture passes across the anterior fossa the lateral frontal towards the sphenoidal fissure, tearing away the region, in the anterior clinoid process, and again comminutes the situation of the roof of the sphenoidal sinus. Progressing onwards, external angular with or without fracturing the posterior clinoid frontal process. process, the fracture passes either along the anterior part of the petrous bone at its junction with the greater wing of the sphenoid towards the opposite middle and external ears, or along the petro-occipital suture to the jugular foramen, and continued along the masto-occipital suture as in the previous case.
[Illustration: FIG. 33. DIAGRAM OF LINES PURSUED BY BASIC FRACTURES. Force applied to the lateral frontal region in the situation of the external angular frontal process.]
3. Force applied to The fracture passes across the roof of the bony the region of the auditory meatus towards the junction of the external ear. anterior and inner walls of the middle ear, the membrane undergoing a variable amount of destruction and displacement. The fracture is then continued across the tegmen tympani, and after following the petro-sphenoidal suture reaches the foramen lacerum medium, being again continued on the opposite side of that foramen to the sphenoidal body. Thence it pursues one of two courses. Most commonly the fracture passes backwards obliquely to the opposite middle and external ears, following a course similar to that already indicated.