184 



SENSORIAL FUNCTIONS. 



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

 concha ; from this there opens a funnel-shaped orifice, ra, 

 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, e, called the 



Fig. 114. 



eustachian tube, leads to the back part of the nostrils, 01 

 roof of the mouth. The parts marked s, v, k, consist of 

 several intricate winding passages called the labyrinth. 

 This part will be explained by another figure. Connected 

 with the ear-drum there is a chain of moveable bones 

 marked 6, which are also explained by another figure. 

 The auditory nerve is seen at n, passing into the centre of 

 the labyrinth 



574. The external ear appears to be formed tor 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 



