THE TEMPORAL BONES. 



69 



double, leading outward and backward to an oblique opening, the hiatus Fallopii, 

 for the passage of the greater petrosal nerve and the petrosal branch of the 

 middle meningeal artery ; 4, a smaller 

 opening, occasionally seen external to the 

 latter, for the passage of the smaller pe- 

 trosal nerve ; 5, near the apex of the bone, 

 the termination of the carotid canal, the 

 wall of which in this situation is deficient 

 in front ; 6, above this canal a shallow de- 

 pression for the reception of the Gasserian 

 ganglion. 



The posterior surface forms the front 

 part of the posterior fossa of the skull, and 

 is continuous with the inner surface of the 

 mastoid portion of the bone. It presents 

 three points for examination : 1. About its 

 centre, a large orifice, the meatus auditorius 

 internus, whose size varies considerably ; its 

 margins are smooth and rounded, and it 

 leads into a short canal, about four lines 

 in length, which runs directly outward and 

 is closed by a vertical plate, the lamina 

 cribrosa, which is divided by a horizontal 

 crest, the crista falciformis, into two un- 

 equal portions. Each portion is subdivided 

 by a little vertical crest into two parts, 

 named respectively anterior and poste- semicircuiar'canaf. 

 The lower portion presents three 



FIG. 34. Diagrammatic view of the Fundus 

 of the internal auditory meatus (Testut): 1. Falci- 

 form crest. 2, Anterior superior cribriform area. 

 2 . Internal opening of the Aquseductus Fallopii. 

 3. Vertical crest which separates the anterior 

 and posterior superior cribriform areas, 4. Pos- 

 terior superior cribriform area, with (4') open- 

 ings for nerve-filaments. 5. Anterior inferior 

 cribriform area. 5'. Spirally arranged, sieve-like 

 openings for the nerves to the cochlea. 5". Open- 

 ing of the central canal of the cochlea. 6. Crest 

 which separates the anterior and posterior infe- 

 rior cribriform areas. 7. Posterior inferior cribri- 

 form area. 7' Orifices for the branches of the 

 nerve to the saccule. 8. Foramen singulare of 

 Morgagni, with the anterior portion of the canal 

 which gives passage to the nerve to the posterior 



nor. 



sets of foramina; one group just below the posterior part of the crest, the area 

 rribrosa media, consisting of a number of small openings for the nerves to the 

 saccule ; below and posterior to this, the foramen singulare, or opening for the 

 nerve to the posterior semicircular canal ; in front and below the first, the tractus 

 spiralis foraminosus, consisting of a number of small spirally arranged openings 

 which terminate in the canalis centralis cochleae and transmit the nerve to the 

 cochlea ; the upper portion, that above the crista, presents behind a series of 

 small openings, the area cribrosa superior, for the passage of filaments to the 

 utricle and superior and external semicircular canal, and, in front, one large 

 opening, the commencement of the aquseductus Fallopii, for the passage of the 

 facial nerve. 2. Behind the meatus auditorius, a small slit, almost hidden by a 

 thin plate of bone, leading to a canal, the aquceductus vestibuli, which transmits 

 the ductus endolymphaticus together with a small artery and vein. In the interval 

 between these two openings, but above them, is an angular depression which lodges 

 a process of the dura mater, and transmits a small vein into the cancellous tissue 

 of the bone. In the child this depression is represented by a large fossa, the 

 floceular fossa, which extends backward as a blind tunnel under the superior 

 semicircular canal. 



The inferior or basilar surface (Fig. 35) is rough and irregular, and forms part 

 of the base of the skull. Passing from the apex to the base, this surface presents 

 eleven points for examination : 1, a rough surface, quadrilateral in form, which 

 serves partly for the attachment of the Levator palati and Tensor tympani 

 muscles ; 2, the large, circular aperture of the carotid canal, which ascends at 

 first vertically, and then, making a bend, runs horizontally forward and inward ; 

 it transmits the internal carotid artery and the carotid plexus; 3, the aquceductus 

 cochlece, a small, triangular opening, lying on the inner side of the latter, close to 

 the posterior border of the petrous portion ; it transmits a vein from the cochlea 

 which joins the internal jugular ; 4, behind these openings a deep depression, the 

 jugular fossa, which varies in depth and size in different skulls ; it lodges the 



