440 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



upper part of the nasopharynx by a wide orifice. 

 Its anterior part, about one inch in length, is enclosed 

 in cartilage, while its posterior portion is encased in 

 bone. The mucous membrane is ciliated and glands 

 are absent. 



3. The Internal Ear. The internal ear is the es- 

 sential part of the 

 organ of hearing 

 and consists of a 

 bony and a mem- 

 branous labyrinth. 

 The latter is 

 contained within 

 the former and 

 represents the 

 same general 

 shape, the two 

 being separated 

 by a lymph space 

 containing the 

 perilymph. A se- 

 ries of cavities 

 constitute the 

 bony labyrinth, 

 which are named 

 from before back- 

 wards cochlea, vestibule, and semicircular canals. 

 The membranous labyrinth situated within these 

 cavities consists of the membranous cochlea, utriculus, 

 and sacculus, and membranous semicircular canals. 



(i) Vestibule, Utriculus, and Sacculus. The vesti- 

 bule forms the central portion of the bony labyrinth 



Fig. 303. Otoscopic view of left 

 membrana tympani : i, Membrana flac- 

 cida; 2, 2', folds bounding the former; 

 3, reflection from processus brevis of 

 malleus; 4, processus longus of incus 

 (occasionally seen) ; 5, membrana tym- 

 pani; 6, umbo and end of manubrium; 

 7, pyramid of light (Morris). 



