THE SKULL 283 



the upwardly directed neck, or meatus audi- 

 torius externus, supports the cartilage of the 

 large external ear. Within the bulla, at the 

 base of the meatus, is an incomplete bony 

 ring, across which the tympanic membrane is 

 stretched during life. 



The Eustachian tube leaves the tympanic 

 cavity by an aperture at the antero-inferior 

 angle of the tympanic bone, between it and the 

 periotic ; and passes forwards to the posterior 

 nasal chamber (p. 311). 



The bony canal by which the facial nerve 

 leaves the skull runs along the posterior 

 border of the tympanic, between it and the 

 mastoid process of the periotic, and opens 

 below at the stylomastoid foramen. 



On the ventral surface of the tympanic 

 bone, near its inner border, is a conspicuous 

 foramen, through which the internal carotid 

 artery enters the skull. 

 iii. The auditory ossicles are most conveniently 

 examined with the bones of the auditory cap- 

 sules, on account of their close connection 

 with the organs of hearing ; though, morpho- 

 logically, they belong to the mandibular and 

 hyoidean arches. 



They form on each side a chain of small 

 bones, stretching across the tympanic cavity 

 from the tympanic membrane to the fenestra 

 ovalis. 



a. The malleus consists of a small body and two 

 processes. The larger process, or manu- 

 brium, is blade-like, and is attached along 

 the greater part of its length to the tym- 

 panic membrane, the tip being near the 

 centre of the membrane. The shorter pro- 

 cess, which is anterior, articulates with a 



