TEMPORAL BONE. 33 



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 process. In front of the vaginal pro- 

 cess is a broad triangular depression, the glenoid fossa, bounded in 

 front by the eminentia articularis, behind by the vaginal process, and 

 externally by the rough lip of the processus auditorius. 



Fig. 19.* 



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 extremity of the inner angle of the glenoid 

 fossa is the foramen of the Eustachian tube ; and separated from it 

 by a thin lamella of bone, called processus cochleariformis, a small 

 canal for the transmission of the tensor tympani muscle. Directly be- 

 hind, and at the root of the styloid process, is the stylo-mastoid fora- 

 men, the opening of exit to the facial nerve, and of entrance to the 

 stylo-mastoid artery. Nearer to the apex of the bone is a large oval 



* A. The reniform fossa of the meatus auditorius interims ; right temporal 

 bone. 1. The ridge dividing the reniform fossa into two compartments. 2. 

 The opening of the aqueeductus Fallopii. The openings following that of the 

 aquaeductus Fallopii in a curved direction require no reference. 3. The cluster 

 of three or four oblique 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, shewing the curved direction 

 of the meatus auditorius externus. 1. The edge of the processus auditorius. 

 2. 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 aquse- 

 ductus Fallopii. 7. Part of the carotid canal. 



C. The annulus membranse tympani or tympanic bone of the foetal skull ; 

 right side. 



D 



