1086 



SPECIAL SENSE ORGANS 



The arteries are branches from the posterior auricular, superficial temporal, and deep 

 auricular arteries (q.v.). The veins and lymphatics connect with those of the auricle and 

 empty similarly'. The nerves are branches from the auriculo-temporal and the auricular 

 ramus of the vagus. 



2. THE MIDDLE EAR 



Under the term middle ear there are included the tympanic cavity (tym- 

 panum), the tympanic antrum and the auditory (Eustachian) tube. These form 

 a continuous irregular passage, filled with air, and located within and upon the 

 surface of the temporal bone. The tympanum is shut off from the external ear 



Fig. 830.- 



-Frozen Coronal Section of the Right Ear. (Somewhat Enlarged.) 



Chorda tympani 



Manubrium mallei / Capitulum mallei 



/ Tympanic cavity 



Stapes / 



, ; 



Facial nerve / 

 . I ' 

 Tympani membxane ] 



Promontorium 



Lamina spiralis ', 



Modiolus * 



/ Dura mater 



/ Temporal bone 



Temporal muscle 



Temporal bone \ 



Cochlea 



Internal carotid 



Internal jugular vein 



Internal carotid artery 



Cartilage of meatus 

 ' External auditory meatus (cartilaginous) 

 Parotid gland 



by the tympanic membrane; and from the chamber which forms the internal ear 

 by the structures which fill in the cochlear and vestibular fcnestrae. It commu- 

 nicates with the pharynx by the auditory (Eustachian) tube. The structures of 

 the middle ear are of importance, and the study is somewhat difficult, on account 

 of the small size of the structures, the depth at which they lie, and the hard charac- 

 ter of the surrounding bone. 



The illustrations (figs. 829, 830, 831, 833, 834) will help to explain the text and should 

 be constantly referred to. Figs. 830 and 831 are taken from frozen sections traversing the 

 right ear in the coronal i)lancs; while figs. 833, 834 represent dissections. 



The parts to be considc^red in order are the tympanic membrane, the tympanic 

 cavity, the tympanic antrum and the auditory (J*]ustachian) tube. 



The Tympanic Mp^mbranp: 



The tympanic membrane [mcml)rana tympanij (fig. 835) is elliptical in shape, 

 its long axis nearly vertical, measuring 9 to 10 mm., its short axis, 8 to 9 mm. 

 It slopes medially from the superior and posterior to the inferior and anterior 



