3$2 Senfe of Hearing, [Book IX,- 



the ear, they have never been able to difcover the 

 peculiar ufes to which all the feveral parts are fubfer- 

 vient. That the concha is clefigned to catch and rever- 

 berate to the auditory tube the vibrations of the air 

 we are certain, from the analogous effect of a fimilar 

 organ, the ear. trumpet. The membrana- tympani, 

 and the little bones of the ear, are faid to have been 

 deftroyed by difeafe, without depriving the patient 

 cf hearing. I cdnnot, however, fuppofe, that any 

 part of the ear is unnecefTary. It therefore feems 

 ieafbnable to believe, that the membrana tympani, 

 which is ftretched acrofs the pafiage to which the 

 vibrations of the air are directed, is defigned to receive 

 them, for which ufe, by its elaftic nature, it is admi- 

 rably fitted. The malleus is attached to the mem- 

 brana tympant, the incus to the malleus ; the oval bone 

 connects one leg of the incus to the head of the ftapes, 

 and the bafis of the latter bone prefies on the feneftra- 

 ovalis. From this ftru&ure we can fcarely draw any 

 Other conclufion, than that the tremulous motion ex- 

 cited in the membrana tympani by the imprefiionsof the 

 air are propagated through the contents of the tym- 

 panum, and imparted to thofe of the labyrinth, which 

 are lined with a delicate nervous film, on which they 

 may operate fo as to produce the ideas of found. 

 When, however, we contemplate the various parts of 

 the labyrinth, we cannot affign any j-eafon for fo 

 complex a flructure, and can only admire it as one 

 of the wonders of creation. The analogy of other 

 animals, indeed, inftructs us in one particular,, viz. 

 that the cochlea is not eflential to hearing, fince birds 

 and fifli hear accurately without this part ; but why it 

 is not eflential remains ftiil a quefticn. 



To confefs, however, that we are ignorant of the 

 means by which we perceive founds, is not more 



humble 



