HEARING. 



.301 



shape than of their office. The first is the malleus, 

 or hammer (m) ; and its long handle (h) is affixed 

 to the centre of the ear-drum : the second is the 

 incus, or anvil (i) ; the third, which is the smallest 

 in the body, being about the size of a millet seed, 

 is the orbicular bone (o) ;* and the last is the stapes, 

 or stirrup (s), the base of which is applied to the 

 membrane of the fenestra ovalis. These bones are 

 regularly articulated together, with all the ordinary 

 apparatus of joints, and are moved by small 

 muscles provided for that purpose. Their office is 

 apparently to transmit the vibrations of the ear- 

 drum to the membrane of the fenestra ovalis, and 

 probably, at the same time, to increase their 

 force. 



The more internal parts of the ear compose what 

 is designated, from the intricacy of its winding 

 passages, the lahi/ri7ith. It is seen at s v k in Fig. 



390, in connexion with the 

 tympanum ; but in Fig. 394, 

 it is represented, on a very 

 large scale, detached from 

 every other part, and sepa- 

 rated from the solid bone in 

 which it lies embedded. It 

 consists of a middle portion, 

 termed the vestibule (v), from 

 which, on its upper and pos- 

 terior side, proceed the three 

 tubes (x, Y, z), called, from their shape, the semi- 



* Blumenbach, and other anatomists, consider this as not being 

 a separate bone, but only a process of the incus ; a view of the sub- 

 ject which is supported by the observations of Mr. Shrapnell, de- 

 tailed in the Medical Gazette, xii. 172. 



