984 



GENERAL STRUCTURE OF EAR. [BOOK in. 



tympanic cavity (Fig. 166 3T. (7.), often called the "middle ear," 

 which through the tubular Eustachian tube (Figs. 166 E.t., 

 169 J7..), opens into the pharynx, and which is lined through- 

 out by mucous membrane continuous with that of the pharynx. 



tnbr-"' 



FIG. 168. THE MEMBRANA TTMPANI. (After Schwalbe.) (Magnified four times.) 



The membrane is seen from the external meatus and the handle of the mal- 

 leus, mbr, is represented as shining through, m.f. the membrana flaccida, the 

 folds of which are represented radiating from p.b., the projection outwards 

 caused by the end of the short process of the malleus, u. the umbo of the mem- 

 brane, to which is attached the end of the handle of the malleus. The figure 

 shews diagrammatically, the radial and circular fibres of the membrane. 



The * internal ear ' forms the mesial side of the more or less 

 flattened and drum-shaped tympanic cavity opposite to the outer 

 side which is to a large extent formed by the tympanic mem- 

 brane ; and at two places the osseous tissue of the bony 

 envelope of the internal ear is wanting, the gaps giving rise 



E.t 



mej 



FIG. 169. DIAGRAM TO ILLUSTRATE THE RELATIONS OF AUDITORY PASSAGE, 

 TYMPANUM AND EUSTACHIAN TUBE. (After Schwalbe.) 



The fieure represents a section not quite horizontal, being inclined down- 

 wards in front ; the right-hand edge of the page may be taken to represent the 

 median plane of the head. 



m.e. external meatus, T. the tympanic cavity. E.t. the Eustachian tube. 

 A. is placed in the antrum mastoideum. m.t. indicates the attachment of the 

 tympanic membrane. 



a.b. the axis of the external meatus, c. b. d. that of the Eustachian tube. 

 dd 1 . shews the curved axis of the antrum. 



