Chap. XX] INTERNAL AND EXTERNAL SENSES 415 



The auricle, except the lower portion, consists of a frame- 

 work of cartilage, containing some fatty tissue and a few 

 muscles. In the lower portion, which is called the lobe, 

 the cartilage is replaced by connective tissue. The auricle is 

 covered with skin, and joined to the surrounding parts by 

 ligaments and a few muscular fibres. It is very irregular in 

 shape, and appears to be an unnecessary appendage to the organ 

 of hearing, except that the central depression, the concha, serves 

 to some extent to collect sound-waves, and to conduct them into 

 the auditory canal. 



The auditory canal is a tubular passage, about an inch (25 mm.) 

 in length, leading from the concha to the drum-membrane. The 



Fig. 193. — Semi-diagrammatic Section through the Right Ear. M, 

 concha ; G, the external auditory canal ; T, tympanic, or drum-membrane ; P, 

 tympanum, or middle ear ; o, oval window ; r, round window. Extending from T 

 to o is seen the chain of the tympanic bones ; R, Eustachian tube ; V, B, S, bony 

 labyrinth ; V, vestibule ; B, semicircular canal ; S, cochlea ; b, I, v, membranous 

 labyrinth in semicircular canal and in vestibule. A, auditory nerve dividing into 

 branches for vestibule, semicircular canal, and cochlea. 



exterior portion of the wall of the auditory canal consists of carti- 

 lage, which is continuous with that of the auricle ; the posterior 

 portion is hollowed out of the temporal bone. This canal is slightly 

 curved upon itself so as to be higher in the middle than at either 

 end, and its direction is forward and inward. Lifting the auricle 

 upward and backward tends to straighten the canal ; except in the 

 case of children it is best straightened by drawing the auricle 



