HEARING. 49 



if there be any imperfection in the hearing of birds. 

 That is easily answered : the hearing of birds is 

 most acute ; the slightest noise alarms ; and the night- 

 ingale, or other bird of song, in a summer evening, 

 will answer to the note of his rival when he is out of 

 hearing. We have next to observe the imperfection 

 in the organ the want of an external ear ; which, 

 were it present, would be at variance with all that we 

 have most to admire in the shape of the bird and the 

 direction of the feathers, as conducing to its rapid 

 passage through the air. With this obvious defect of 

 the external ear, can we admit that the internal ear is 

 also imperfect, notwithstanding the very remarkable 

 acuteness of hearing, which we know to result from 

 this internal structure, and from it alone? Now we 

 we do, in fact, find a different structure in the ear of 

 birds, but yet nothing is wanting. The columella is 

 a shaft of bone of exquisite delicacy, which is extended 

 from the outward membrane of the ear to the laby- 

 rinth, or proper seat of the nerve of hearing. It oc- 

 cupies the place and office of the chain of four bones 

 which belong to the ear of mammalia. We have no 

 authority, however, for affirming that the incus is here 

 wanting, more than any other bone of the chain ; 

 and if it be said that the os quadratum is the missing 

 incus, why should not we find in the oviparous rep- 

 tiles, where there is a columella in the ear, an os qua- 

 dratum in the jaw ? 



" From this mode of inquiry we find that the sense 

 of hearing is enjoyed in an exquisite degree in birds; 

 that the organ of the sense is not imperfect, but is 

 adapted to a new construction, and a varied appara- 

 tus, suited to the condition of the bird ; and that there 

 is no accidental dislocation, or substitution of some- 

 thing less perfect than what we find in other classes 

 of animals*." 



* Bridgewater Treatise on the Hand, p. 139. 



