126 



OSTEOLOGY. 



downwards from the inferior surface of the posterior root there is a conical process, 

 called the post-glenoid tubercle, which forms a prominent anterior lip to the lateral 

 extremity of the petro-tympanic fissure ; it is the representative in man of a 

 process which is developed in some mammals and prevents the backward displace- 

 ment of the mandible. By some anatomists it is referred to as the middle root 

 of the zygomatic process. 



The zygomatic process by its inferior margin and medial surface gives origin to 

 the masseter muscle, whilst attached to its superior edge are the layers of the 

 temporal fascia. Behind the external acoustic meatus, and below the supramastoid 

 crest, the squainous element extends downwards as a pointed process, which assists 

 in forming the roof and posterior wall of the external acoustic meatus, where 

 it unites inferiorly with the tympanic part and forms the lateral wall of a hollow 

 within called the tympanic antrum. In the adult this process is occasionally 



Groove for middle 

 temporal artery 



Temporal surface 



Parietal notch 



Supra-meatal spine 



Zygomatic process 



Tuberce at root of zygoma 



Tuberculum articulare 



Remains o 



masto-squamosal 



suture 



Mastoid process 



External acoustic meatus Tympano- External processus^ 

 mastoid acoustic styloidei 

 fissure process 



Styloid process 



FIG. 136. THE RIGHT TEMPORAL BONE SEEN FROM THE PARIETAL SIDE. 



The squamo-zygomatic part is coloured blue ; the petro-mastoid, red. 

 The tympanic part and styloid process are left uncoloured. 



sharply defined posteriorly by an oblique irregular fissure, the remains of the masto- 

 squamosal suture. Immediately above and behind the external acoustic meatus 

 there is often a little projecting spur of bone, the spina suprameatum (supra- 

 meatal spine). 



The angular recess between this process and the supramastoid crest is of interest 

 surgically, a-nd is known as Mace wen's triangle. The same authority has pointed out that 

 the masto-squamosal suture frequently remains open till puberty and occasionally after, 

 and may be of importance as a channel along which infective processes may extend. 



The cerebral surface of the squamous part, less extensive than the parietal aspect 

 owing to the bevelling of the parietal border, is marked by the impression of the 

 gyri of the temporal lobe of the cerebrum, and is limited below by the petro- 

 squamosal suture, the remains of which can frequently be seen. It is crossed in 

 front by an ascending groove for the posterior branch of the middle meningeal 

 artery and its accompanying vein, branches from which course backwards over the 

 bone in grooves more or less parallel to its parietal border. 



The parietal border of the squamous part is curved, sharp, and scale-like, being 



