USES OF THE PARTS IN THE EAR. 325 



XXI. 



REVIEW OP THE USES OF THE PARTS IN THE EAR. 



We find late physiological writers acknowledg- 

 ing their ignorance of the functions of the partic- 

 ular structures in this organ ; and we cannot there- 

 fore conceal that there is a difficulty in assigning 

 the uses of the parts. Nevertheless, we shall now 

 endeavour to explain our conceptions of this mat- 

 ter; and, at all events, there is enough to prove the 

 main argument of design and of the fine adapta- 

 tion of this organ to the laws by which sound is 

 propagated. 



The outward ear of man and animals is so ob- 

 viously provided for collecting sound that there 

 can be no cavil here. It is extended and ;novea- 

 ble in those animals which hear acutely, and in 

 some, as the bat, it is double, consisting of one 

 expanded membrane within the other. And this 

 brings to mind an assertion, that the membrane 

 of the tympanum is affected by the vibrations of 

 the side of the auditory tube more than by the di- 

 rect impulse of the atmosphere against it ; for if 

 there be one conical expanded external car with- 

 in another, it is obvious that there must be a larger 

 surface to receive vibrations and communicate 

 them to the tube and membrane of the tympanum. 

 29 



