SECT. XIV. 4. PRODUCTION OF IDEAS. 125 



tion : fo the mufcles and bones of the ear feem 

 adapted to increafe or diminifh the tenfion of the 

 tympanum for the purpofes of fimilar mechanical 

 vibrations. 



But it appears from direction, that the tympa- 

 num is not the immediate organ of hearing, but 

 that like the humours and cornea of the eye, it is 

 only of ufe to prepare the object for the immediate 

 organ. For the portio mollis of the auditory nerve 

 is not fpread upon the tympanum, but upon the 

 veftibulum, and cochlea, and femicircular canals 

 of the ear ; while between the tympanum and the 

 expanfion of the auditory nerve the cavity is faid 

 by Dr. Cotunnus and Dr. Meckel to be filled with 

 water ; as they had frequently obferved by freez- 

 ing the heads of dead animals before they diflected 

 them ; and water being a more denfe fluid than 

 air is much better adapted to the propagation & 

 vibrations. We may add, that even the external 

 opening of the ear is not abfolutely neceiTary for 

 the perception of found : for fome people, who 

 from thefe defects would have been completely deaf, 

 have diftinguifhed acute or grave founds by the 

 tremours of a flick held between their teeth pro- 

 pagated along the bones of the head, (Haller. Phyf. 

 T. V. p. 295). 



Hence it appears, that the immediate organ of 

 hearing is not affefted by the particles of the air 

 themfeives, but is ftimulated into animal motion 

 by the vibrations of them. And it is probable from 

 the loofe bones, which are found in the heads of 

 fome fifties, that the vibrations of water are fenfi- 

 ble to the inhabitants of that element by a fimilar 

 organ. 



The motions of the atmofphere, which we be- 

 come acquainted with by the fenfe of touch, are 

 combined with its folidity, weight, or vis inertise ; 

 whereas thofe, that are perceived by this organ, 



K 2 depend 



