792 HEARING, SMELL, AND TASTE. 



papillary prominence called the tragus ; posterior to this, separated by a 

 fissure, is the antitragus, which is a continuation of the helix. On the 

 inferior portion of the pinna is a soft pendulous portion, termed the 

 lobule. The meatus leads from the concha to the middle ear, from which it 

 is separated by the tympanic membrane. Its direction is forward, inward, 

 and slightly upward ; its lower surface being longer than the upper, on ac- 

 count of the obliquity of the position of the tympanic membrane. The canal 

 consists of an external membrano-cartilaginous portion, which is continuous 

 with the pinna, and an internal osseous portion formed by the mastoid bone. 

 In the external portion of the canal are found numerous hairs and seba- 

 ceous glands ; in the internal portion are found the ceruminous glands, which 

 secrete a peculiar substance commonly known as the earwax. 



697. The middle ear or tympanum is an irregular flattened cavity, 

 situated in the petrous portion of the temporal bone, and lined with a mu- 

 cous membrane. It is separated from the meatus by a membranous dia- 

 phragm, which is the tympanic membrane ; and from the internal ear by an 

 osseo-membranous partition, which forms a common wall for both. Through 

 the Eustachian tube it communicates with the pharynx. On its posterior 

 wall are seen orifices of the mastoid cells. The tympanic membrane is a 

 semi-transparent oval membrane, concave on its external and convex on its 



FIG. 186. 



FIG. 187. 



Natural size. 



Interior of the Osseous Labyrinth. (After Sommerring.) V, vestibule ; av, aqueduct of the 

 vestibule; o, fovea hemielliptica ; ?, fovea hemispherica ; S, semicircular canals; s, superior; p, 

 posterior; i, horizontal; a, a, a, the ampullar extremity of each; C, cochlea; etc, aqueduct of the 

 cochlea ; sv, osseous zone of the lamina spiralis, above which is the scala vestibuli, communicat- 

 ing with the vestibule ; st, scala tympani below the spiral lamina. 



internal surface, where it has attached the long process of the malleus, one 

 of the ossicles. It is placed in an oblique position, sloping downward, for- 

 ward, and inward at an angle of about 45. Its circumference is attached 

 to a groove in the temporal bone. In the fetus this portion of the bone 

 exists as a separate piece, called the tympanic bone (Fig. 184), but it after- 

 ward becomes ossified to the temporal. The tympanic membrane consists 

 of three layers the external, middle, and internal. The external is a 

 continuation of the integument covering the meatus ; the internal is a con- 

 tinuation of the mucous membrane lining the tympanum ; the middle layer, 



