TEMPORAL BONE. 67 



five openings, the two upper ones being the largest, and occupying the 

 superior compartment of the reniform fossa, and the two or three inlerioi 

 ones, smaller than the upper, the inferior compartment. Behind the 

 latter, at the distance of a line and a half, and on the posterigr wall of the 

 meatus, is a cluster of three or four oblique openings, two of which are 

 minute. The inferior and larger compartment of the reniform fossa pre- 

 sents a well-marked spiral groove, which commences on the convex border 

 of the fossa, immediately below the line of openings above described, and, 

 sweeping round the convexity of the inferior compartment, and becoming 

 deeper as it proceeds, terminates by a small round aperture in the centre 

 of the spire- The uppermost of the openings of the reniform fossa is the 

 aperture of the aquseductus Fallopii, and gives passage to the facial nerve. 

 The rest are cul de sacs, pierced at the bottom by a number of minute 

 foramina for the passage of filaments of the vestibular nerve, while the 

 cluster of three openings on the posterior wall of the meatus are intended 

 for single filaments of the same nerve. The spiral groove corresponds 

 with the base of the cochlea, and being pierced by a number of minute 

 foramina for filaments of the cochlear nerve, is named tractus spiralis 

 foraminulentus. The opening in the centre of the spiral impression leads 

 into a canal \vhich occupies the central axis of the .nodiolus, and is thence 

 called tubulus centralis modioli. 



The basilar surface is rough and irregular, and enters into the formation 

 of the under surface of the base of the skull. Projecting downwards, near 

 its middle, is a long sharp spine, the styloid process, occasionally connected 

 with the bone only by cartilage, and lost during maceration, particularly 

 in the young subject. At the base of this process is a rough sheath-like 

 ridge, into which the styloid process appears implanted, the vaginal pro- 

 cess. In front of the vaginal process is a broad triangular depression, the 

 glenoid fossa, bounded in front by the erninentia articularis, behind by 

 the vaginal process, and externally by the rough lip of the processus audi- 

 torius. 



This fossa is divided transversely by the glenoid fissure (fissura Glaseri), 

 which lodges the extremity of the processus gracilis of the malleus, and 

 transmits the laxator tympani muscle, chorda tympani nerve, and anterior 

 tympanic artery. The surface of the fossa in front of this fissure is smooth, 

 to articulate with the condyle of the lower jaw ; and that behind the fissure 

 is rough, for the reception of a part of the parotid gland. At the extre- 

 mity of the inner angle of the glenoid fossa is the foramen of the Eusta- 

 chian tube ; and separated from it by a thin lamella of bone, called pro- 

 cessus cochleariformis, a small canal for the transmission of the tensor 

 tympani muscle. Directly behind, and at the root of the styloid process, 

 is the stylo-mastoid foramen, the opening of exit of the facial nerve, and 

 of entrance of the stylo-mastoid artery. Nearer the apex of the bone is a 



openings on the posterior wall of the meatus. 4. The spirally-grooved base of the 

 cochlea. 



B. A section of the temporal bone, right side, showing the curved direction of the 

 meatus auditorius externus. 1. The edge of the processus auditorius. *,. The groove 

 into which the membrana tympani is inserted. The obliquity of the line from 2 to 3 

 indicates the oblique termination of the meatus, and the consequent oblique direction, 

 of the membrana tympani. 4, 4. The cavity of the tympanum. 5. The opening of 

 the Eustachian tube. 6. Part of the aquaeductus Fallopii. 7. Part of the carotid 

 canal. 



c. The annulus membranse tympani or temporal bone -f the foetal skull, right side. 



