The Special Senses 



265 



415. The Auditory Canal. The auditory canal, the pas- 

 sage to the middle ear, conducts the vibrations of sound 

 to the tympanic membrane. It is about an inch and a 

 quarter long. Near its outer portion are a number of fine 

 hairs slanting outwards. These prevent the entrance of 

 insects. Embedded in the deeper parts of the canal are 



FIG. 140. General View of the Organ of Hearing. 



A, pinna; B, cavity of the concha, showing the orifices of a great number of 

 sebaceous glands; C, external auditory meatus; D, membrana tympani; 

 F, incus; If, malleus; 1C, handle of malleus applied to the internal surface 

 of the membrana tympani; L, tensor tympani muscle; between M and K 

 is the tympanic cavity ; N, Eustachian tube ; O, P, semicircular canals ; 

 R, internal auditory canal; S, large nerve given off from the facial gan- 

 glion ; T, facial and auditory nerves. 



glands which secrete the cerumen, or earwax, which keeps 

 the canal moist and helps to protect it against foreign 

 bodies and insects. 



416. The Middle Ear. At the inner end of the outer 

 ear passage is the middle ear or tympanum, or "the drum 

 of the ear." Stretched at an angle across the deep end 

 of the passage is a thin oval membrane which completely 

 closes it. 



