THE TEMPORAL BOXES 37 



and a })roc('SS of dura niatcT. Occasionally a l»ri.stle can 1)0 passed along this pas- 

 sage into the vestibule. Above, and anterior to this, is a second slit also lodging a 

 process of the dura mater. This is a remnant of the floccular fossa, so conspicu- 

 ous in the f<ptus. Posteriorly, this surface has a deep groove for the lateral sinus. 



The anterior face of the pyramid is sci)arated from the squamosal by the 

 petro-squamous suture, wliicli may })ersist throughout life. It presents the 

 following points of interest: near the apex it has a shallow dei)ression for the Gas- 

 serian ganglion, and the recess of dura mater (Meckel's cave) in Avhich it lies. 

 Behind these are two small foramina, overshadowed by a thin osseous lip. Of these, 

 the larger and more internal is the hiatus Fallopii, wliich transmits a small artery 

 from the middle meningeal and the greater petrosal nerve. The smaller and exter- 

 nal foramen is for the lesser petrosal nerve. Still more externally there is a thin 

 translucent plate of bone, the tegmen tympani. Behind, and slightlv internal to 

 this, there is a ridge formed l)y the superior semicircular canal. 



The inferior or basilar surface is very irregular, and has the following points 

 of interest. At the apex is a quadrilateral smooth space for the tensor ti/mjimii and 

 levator palnti muscles. Behind this is the large circular orifice of the carotid canal, 

 for the transmission of the carotid artery and a plexus of sympathetic nerves. 

 Internal to this, near the inner border of the bone, is the orifice of the aqueductus 

 cochleae nluetus perilymphaticus). In the adult it transmits a small vein from 



Fig. Ui. — Tin-; Lkit Tk.mpok.vl Boxk. (Inferior view.) 



CAROTID CANAL ■ 



SURFACE FOR SPHENOID 



Tensor tympani and 



levator palati 



TYMPANIC CANALICULUS 



AQUEDUCTUS COCHLE/t 

 AURICULAR CANALICULUS . . .^^ 



JUGULAR FOSSA ^I^^: j) 



JUGUUR SURFACE 

 STYLO-MASTOID FORAMEN 



ARTICUUTION FOR OCCIPITAL 



OCCIPITAL GROOVE 



ARTICULAR EMINENCE 



ZYGOMATIC TUBERCLE 

 GLASERIAN FISSURE 

 STYLOID PROCESS 

 EXTERNAL AUDITORY MEATUS 

 AURICULAR FISSURE 



MASTOID PROCESS 

 DIGASTRIC GROOVE 



the cochlea to the internal jugular. Posteriorly is the elli])tical jugular fossa with 

 smooth walls for the ampulla which receives the lateral and inferior ixtrosal sinuses. 

 and forms the commencement of the internal jugular vein. In the ridge of bone 

 between the fossa and the carotid canal there is a small foramen, the tympanic 

 canaliculus, for the tympanic branch of the glosso-jjliaryngcal nerve. On the 

 outer wall of the fossa a similar minute foramen, the auricular canaliculus, ])er- 

 mits the jtassage inwards of the auricular branch (Arnold's nen-e) of the vagus 

 nerve. Bcidnd the fossa is the rough jugular surface, which receives the jugular 

 process of the occipital. Firmly ankylosed to the inner surface of the tympanic 

 plate is the styloid process, varying in length from one to five cm. At its base 

 is the stylo-mastoid foramen, from which Lssues the facial ner\'e; the stylo- 

 mastoid artery enters the Fallopian canal through this opening. Running back- 

 wards from this foramen are two grooves; the outer is the digastric groove, 

 from which the digastric muscle arises. The inner is narrower and shallower: 

 it lodges the occipital artery. 



Of the outer surface, the only part which appears externally is the mastoiil 

 process; the rest is occupied by a recess known as the tympanum. The mastoid 

 process is a nij)] de-shaped prominem-e of bone. fornie<i jiartly by the sipiamosal, 

 l)Ut mainly by the petrosal. Its ujjjjcr limit is the supra-mastoid crest. Below 

 the crest an irregular furrow crosses the surface of the process from the jxirietal 



