188 



SENSORIAL FUNCTIONS. 



External Ear. The external Ear, c, is called the 

 concha : from this there opens a funnel-shaped orifice, 

 m, called the meatus auditorius, or orifice of the Ear, 

 which leads to the internal parts. At the internal 

 extremity of this orifice, and which it closes, is situated 

 the Ear-drum, d, called the tympanum. Behind the Ear- 

 drum there is a hollow space, t, called the cavity of the 

 tympanum. From this cavity, a trumpet-shaped tube, 



Fig. 114. 



e, called the Eustachian tube, leads to the back part of 

 the nostrils, or roof of the mouth. The parts marked 

 s, v, It, consist of several intricate winding passages call- 

 ed the labyrinth. This part will be explained by another 

 figure. Connected with the Ear-drurn there is a chain 

 of moveable bones marked b, which are also explained 

 by another figure. The auditory nerve is seen at n, 

 passing into the centre of the labyrinth. 



The external Ear appears to be formed for the pur- 

 pose of collecting the sonorous undulations of the air, 

 and of directing them through the canal to the Ear- 

 drum. 



The Ear-drum is stretched across the meatus, or ori- 

 fice of the Ear, like the skin of a drum, whence its 

 name; and it performs a corresponding office ; for the 



