THE SKULL. 303 



angle of the tympanic bone, between it and the 

 periotic, and passes forwards to the posterior 

 nasal chamber (p. 375). 



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. 



The auditory ossicles (see fig. 64) are most 

 conveniently examined with the bones of the 

 auditory capsules, on account of their close 

 connection with the organs of hearing ; 

 though, morphologically, they belong to the 

 mandibular and liyoidean arches. 



They form on each side a chain of small 

 bones stretching across the tympanic cavity 

 from the tympanic membrane to the fenestra 

 ovalis. 



1. The malleus consists of a small body and two 

 processes. The larger process, or manu- 

 brium, is blade-like, and is a'ttaehed 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 

 small fossa on the inner surface of the 

 tympanic bone. 



3. The incus is a minute somewhat pyriform 

 bone : its head bears in front a saddle- 

 shaped articular surface for the body of 

 the malleus, and is produced behind into 

 a short process, which articulates with a 



