THE TEMPORAL BONE 



69 



and tympanic, and a knowledge of their arrangement in the early stages of growth greatly 

 facilitates the study of the fully formed bone. 



The more important division of the temporal bone is the petrous portion. It 

 is pyramidal in shape, and contains the essential part of the organ of hearing, 



Fig. 88. — The Temporal Bone at Birth. 



Squamosal 



Tympanic 



Petrosal 



Fig. 89. — Temporal Bone at Birth. 

 (Inner view.) 



Hiatus canalis facialis 



Floccular fossa 

 ^quaeductus vestibuli 

 Internal auditory 

 meatus 



Fig. 90. — The Temporal Bone at Birth. (Outer view.) 



Post-glenoid tubercle — 

 Petro-tympanic fissure 

 Tympanic annulus 



Petro-squamous suture 

 Petrosal 



Stylo-mastoid foramen 

 Tympano-hyal 



Carotid canal 



Fig. 91. — Right Temporal Bone at about Six Years. 



The tympanic plate has been separated and drawn below. A portion of the post-auditory 



process of the squamosal has been removed to show the mastoid antrum. 



Position of lateral semicircular canaly 



Mastoid antrum 



Fenestra vestibuli 

 Canal for tensor tympani 

 Promontory 



^ Carotid canal 



Mastoid process 

 Fenestra cochleae 



— Non-ossified area of the 

 tympanic plate 



Tympanic 



around which it is developed as a cartilaginous capsule. This is known as the 

 periotic capsule or petrosal element, and its base abuts on the outer aspect of the 



