38 



rilK SKELETOX 



notch downwards, to the middle of the meatus. Tliis furrow (squamo-mastoid) is 

 often dott(Ml witli holes, and represents the line of union of squamosal and petrosal. 

 The mastoid }»rt)eess <rives attaehment to the sterno-maMoid, .splenius capitis, trachelo- 

 iiia-'<t<ii(L occlpito-froiitdlis. and retvdhens aurem muscles. 



The tympanum is hidden hy the tympanic pl<tt(\ which extends downwards 

 from the Glaserian fissure to form the vaginal process. Anteriorly it extends 

 forwards and ankyloses with the outer wall of the carotid canal. The Glaserian 

 fissure separates it from the squamosal. This fissure transmits the tympanic 

 branch of the internal maxillary artery, and lodges the slender process of the 

 malleus. A narrow subdivision of this fissure, canal of Huguier, is traversed 1)y 

 the chorda tympani nerve. The tympanic i)late forms the anterior, lower, and 

 part of the posterior walls of the external auditory meatus. It is limited poster- 

 iorlv by tlie auricular lissure, through which the auricular twig of the vagus nerve 



issues. 



The external auditory meatus assumes the form of an elliptical bony tube. 

 Its outer margin is rough and gives attachment to the cartilaginous portion of the 

 pinna. Between the posterior edge of the meatus and the mastoid process is the 

 auricular fissure. The tympanic orifice of the meatus is smooth, and presents a 



Fio. 47.— Temporal Bone with Muscle Attachments. 



TYMPANIC PLATE 



Stylo-glossus Stylo-pharyngeu8 



Stylo-hyoid 



Retrahens aurem 

 Oceipito-fron talis 



Sterno-inastoid 



Trachelo-mastoid 

 Splenius capitis 



well-marked groove for the tympanic membrane. This is very conspicuous in 

 young bones. The direction of the meatus is somewhat oblique. In children, and 

 occasionally in adults, a circular opening exists in the anterior wall of the meatus 

 (Hg. r,.S). 



Articulations. — The temporal bone articulates Avith the occipital, parietal, 

 sphenoid, malar, and by a movalde joint with the mandi1)l(\ Occasionally the 

 sfjuamosal presents a process which articulates with the frontal. A fronto- 

 squamosal suture is common in the skulls of the lower races of nu'n, and is 

 normal in the skulls of the chimpanzee, gorilla, and gibbon. 



The muscles connected with the temj)oral bone are: — 



To the mastoid process 



Stemo-mnstoid. 

 Splenius capitis. 

 Trachelo-mastoid. 

 Digastric. 

 Occipito-frontalis. 

 Retrahens aurem. 



