196 SENSORIAL FUNCTIONS. 



under the tympanum containing air ; this part of the 

 apparatus being obviously fitted for atmospheric hearing, 

 as the other apparently is for aquatic hearing only. 



What clear marks of design and what wonderful tra- 

 ces of wisdom and goodness is evinced in the adapta- 

 tion of these parts to the wants and habits of these poor 

 cold blooded animals ! Truly, " an undevout naturalist 

 must be mad." 



Hearing in Birds. In the Birds there is a cavity 

 beyond the tympanum, as in man, and the tympanum 

 itself, instead of being on the outside, lies concealed in 

 a short tube, without any external ear, thus placing this 

 class, in respect to the auditory apparatus, between the 

 Amphibia and Quadrupeds. 



The ear of man may be taken as an example of the 

 interior structure of this organ in the whole of the oth- 

 er Mammalia. In Quadrupeds, the chief peculiarity in 

 other respects is in the size and form of the external 

 ear ; and from a comparison of the relative size of 

 this part in the various tribes, it has been inferred, that 

 it bears a tolerably constant proportion to the degree of 

 acuteness of hearing, and consequently that it contrib- 

 utes essentially to that faculty. Thus in the rabbit, 

 where the cochlea is uncommonly long, and somewhat 

 trumpet-shaped, the hearing is remarkably acute. In 

 the dog and horse this part is well developed, and we 

 accordingly find a corresponding acuteness of hearing. 



In animals with long ears, there are muscles for the 

 purpose of erecting or turning them towards the point 

 whence the sound proceeds ; and thus they have the 

 effect of an ear trumpet, in concentrating the sono- 

 rous undulations, from whatever direction they come. 

 Every one must have observed the employment of this 

 faculty in the horse, which always turns his ear in the 

 direction of the sound. Hence it is, that the leaders of 

 coach horses turn their ears forward, while those 



What is said of the ears of birds 7 What is the construction of the 

 internal ear of the mammalia 7 Is there any relation between the exter- 

 nal ears of animals, and their sense of hearing 7 Do men ever possess 

 the power of turning their ears 7 



