THE EAR. 



423 



the attollens, attrahens, and retrahens aurem. The 

 intrinsic muscles pass between the different parts of 

 the pinna ; they are 

 named the helicus 

 major and minor, the 

 tragicus and anti- 

 tragicus, the trans- 

 verse and the oblique. 

 The auditory canal, 

 or meatus auditorius 

 externus, is also a 

 portion of the exter- 

 nal ear ; it extends 

 from the concha to 

 the membrana tym- 

 pani, and presents an 

 external cartilaginous 

 and an internal osseous 

 portion, and is, there- 

 fore, an osseo-cartilagi- 

 nous canal, cylindroid 

 in form. Its vertical 

 diameter externally exceeds the transverse at the mem- 

 brana tympani. The transverse diameter is the greatest; 

 it is about one and a quarter inches 

 long, and runs forward, inward, and 

 curves slightly upward. Its inner 

 extremity presents a groove for the at- 

 tachment of the tympanic membrane. 

 This groove is complete, except the 

 superior portion, where it is notched. 

 The skin lining this canal is thin and 

 tightly adherent, and externally presents a number of 

 sebaceous glands, which form the cerumen, or ear-wax. 



FIG. 182. EXTERNAL, MIDDLE, AND 

 INTERNAL, EAR. 



1, external ear : 2, middle ear; 3, internal ear; 4, pinna; 

 5, helix; 6. autihelix; 7, fossa navicnlaris : 8, fossa innomi- 

 nata; 9. tragns: 1U. antitragus : 11, concha; 12. lobe; 13, 

 in eat us auditorius externus; 14, tympanic membrane; 15, 

 promontory ; 16, foramen rotnndum*; 17, posterior wall of the 

 tympanum; 18, ogsicula auditus; 19, Eustachian tube; 20, 

 narrow canal, containing the tensor tympani muscle; 21, 

 vestibule ; 22. semicircular canals, the superior, posterior, 

 and horizontal; 23. ampullae; 24, cochlea; 25. prominence 

 caused by the scala vestibuli ; 26, scala tympani. 



FIG. 183. THE PINNA. 



