68 



OSTEOLOGY. 



inwards it terminates at the commencement of a well-marked fissure, the Glaserian 

 fissure ; whilst the posterior root, which is strongly marked, runs from the upper 

 border of the zygoma, in an arched direction, upwards and backwards, forming the 

 posterior part of the temporal ridge. At the junction of the anterior root with 

 the zygoma is a projection, called the tubercle, for the attachment of the external 

 lateral ligament of the lower jaw ; and between the anterior and middle roots is 

 an oval depression, forming part of the glenoid fossa (y^fa, a shallow pit), for the 

 reception of the condyle of the lower jaw. This fossa is bounded, in front, by the 

 eminentia articularis ; behind, by the vaginal process ; and, externally, by the 

 auditory process, and middle root of the zygoma ; and is divided into two parts 

 by a narrow slit, the Glaserian fissure : the anterior part, formed by the squamous 

 portion of the bone, is smooth, and covered in the recent state with cartilage, and 

 articulates with the condyle of the lower jaw. This part of the glenoid fossa is 

 separated from the auditory process, by a small tubercle, the post-glenoid process, 



Fig. 31. Left Temporal Bone. Inner Surface. 



the representative of a prominent tubercle which, in some of the mammalia, 

 descends behind the condyle of the jaw, and prevents it being displaced backwards 

 during mastication (Humphry). The posterior part of the glenoid fossa is formed 

 chiefly by the vaginal process of the petrous portion, and lodges part of the parotid 

 gland. The Glaserian fissure, which leads into the tympanum, lodges the pro- 

 cessus gracilis of the malleus, and transmits the Laxator tympani muscle and the 

 anterior tympanic artery. The chorda tympani nerve passes through a separate 

 canal parallel to the Glaserian fissure (canal of Huguier), on the outer side of the 

 Eustachian tube, in the retiring angle between the squamous and petrous portions 

 of the temporal bone. 



The internal surface of the squamous portion (fig. 31) is concave, presents 

 numerous eminences and depressions for the convolutions of the cerebrum, and 

 two well-marked grooves for branches of the middle meningeal artery. 



Borders. The superior border is thin, bevelled at the expense of the internal 

 surface, so as to overlap the lower border of the parietal bone, forming the 



