the roof and posterior wall of the external auditory meatus, where it unites 
inferiorly with the tympanic plate. In the adult this process is occasionally 
sharply defined posteriorly by an oblique irregular fissure, the remains of the 
masto-squamosal suture. 
112 OSTEOLOGY. 
Professor Macewen has pointed out that this suture frequently remains open till 
puberty and occasionally after, and may be of importance as a channel along which in- 
fective processes may extend. 
The inner surface of the squamous part, less extensive than the outer aspect 
owing to the bevelling of the superior border, is marked by the impression of the 
convolutions 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 middle meningeal artery, branches from 
which course backwards over the bone in grooves more or less parallel to its upper 
border. 
Eminence of superior 
semicircular canal 
Groove for middle 
meningeal artery 
Groove for superior 
petrosal sinus 
Mastoid 
foramen 
Groove for lateral sinus 
Aqueduct of the vestibule 
Internal auditory meatus 
Aqueduct of the cochlea 
inner surface of mastoid process 
Styloid process 
Fic. 86.—RicHt TEMPORAL Bone (Inner Side). 
The superior border of the squamous part is curved, sharp, and scale-like, being 
bevelled at the expense of its inner table, except in front, where the margin is thick 
and stout. Here it articulates with the great wing of the sphenoid, its union with 
that bone extending to near the fore part of the summit of the curv e, behind which 
it is united to the parietal overlapping the lower border of that bone; posteriorly 
the free margin of the si juamous part ends at an angle formed between it and the -- 
mastoid process called the incisura parietalis. 
The tympanic part (pars tympanica) of the temporal bone forms the anterior, 
lower, and part of the posterior wall of the external auditory meatus. Bounded 
in front and above by the Glaserian fissure, it forms the hinder wall of the non- 
articular part of the elenoid fossa. Fused internally with the petrous part, its 
lower edge, sharp and well defined internally, splits to enclose the root of the 
projecting styloid process, and is hence called the vaginal process. Externally it 
unites with the fore part of the mastoid process, and higher up with the descending 
process of the squamous part, from both of which it is “separated by the auricular 
fissure (fissura tympano-mastoidea) through which the auricular ‘branch of the 
vagus escapes. Its free border, which forms the anterior, lower, and part of the 
