SPECIAL SENSES 



communicates with the mastoid antrum, into which open little canals 

 leading to the mastoid cells. The tympanum also presents an opening 

 leading to the Eustachian tube and a small foramen that gives passage 

 to the tendon of the stapedius muscle. The Eustachian tube extends 

 from the upper part of the pharynx to the tympanum. 



The small bones of 

 the ear are three in 

 number the mal- 

 leus, the incus and the 

 stapes, forming a 

 chain and connected 

 together by ligaments 

 (Fig. 1 86). These 

 bones are situated in 

 the upper part of the 

 tympanum. The han- 

 dle of the malleus 

 (II, 3, Fig. 1 86) is 

 closely attached to 

 the membrana tym- 

 pani, and the long 

 process (II, 2, Fig. 

 1 86) is attached to 

 the Glasserian fissure 

 of the temporal bone. 

 The malleus is articu- 

 lated with the in- 

 cus. The incus (I, 2, 

 Fig. 1 86) is connected 

 with the posterior wall 

 of the tympanum, 

 near the openings of 

 the mastoid cells. It 

 is articulated with the 

 malleus, and by the 

 extremity of its long 

 process, with the stapes. The stapes (I, 3, Fig. 186) is the most internal 

 bone of the middle ear. It is articulated by its smaller extremity with 

 the long process of the incus. Its base is oval and, with its annular 

 ligament, is applied to the fenestra ovalis. The direction of the stapes 

 is nearly at a right angle with the long process of the incus, in 'the 

 natural state. Some anatomists describe a fourth bone as existing be- 



Fig. 185. General view of the organ of hearing (Sappey). 



I, pinna; 2, cavity of the concha, on the walls of which are seen 

 the orifices of a great number of sebaceous glands; 3, external audi- 

 tory meatus ; 4, angular projection formed by the union of the an- 

 terior portion of the concha with the posterior wall of the auditory 

 canal; 5, openings of the ceruminous glands, the most internal of 

 which form a curved line which corresponds with the beginning of 

 the osseous portion of the external meatus; 6, membrana tympani 

 and the elastic fibrous membrane which forms its border; 7, anterior 

 portion of the incus; 8, malleus; 9, handle of the malleus, applied to 

 the internal surface of the membrana tympani, which it draws in- 

 ward toward the projection of the promontory; 10, tensor-tympani 

 muscle, the tendon of which is reflected at a right angle, to become 

 attached to the superior portion of the handle of the malleus; n, 

 tympanic cavity; 12, Eustachian tube, the internal or pharyngeal ex- 

 tremity of which has been removed by a section perpendicular to its 

 curve ; 13, superior semicircular canal ; 14, posterior semicircular 

 canal; 15, external semicircular canal; 16, cochlea; 17, internal 

 auditory canal; 18, facial nerve; 19, large petrosal branch, given off 

 from the ganglioform enlargement of the facial and passing below 

 the cochlea, to go to its distribution ; 20, vestibular branch of the 

 auditory nerve; 21, cochlear branch of the auditory nerve. 



