[ 163 ] 



SECT. XVI 



OF HEARING. 



247. Sound, which is excited by the collision of 

 elastic bodies and propagated by the air, is perceived 

 by the sense of hearing,* and is first received by the 

 conchiform cartilaginous external ear,f which few of 

 our countrymen have the power of moving. J By this 

 it is collected; then conveyed into the meatus audi- 

 torius, which is anointed by a bitter cerumen ; § (A) 

 and strikes against the membrana tympani, which is 

 placed obliquely in a circular furrow of the temporal 

 bone and separates the meatus from the internal ear. 



248. Behind this membrane lies the middle portion 

 of the ear, — the cavity of the tympanum, whose fundus 

 is directed upwards and inwards. 



It contains three || ossicula auditus: of which the 

 exterior, or malleus, adheres by its manubrium to the 

 membrana tympani, is generally united in the adult 



* Sommerring, Abildung desmenschlichen H'dror gans. Franckfurt.180fi.fol. 



•f B. S. Albinus, Annotat. Academ. L. vi. tab. iv. 



J J. Rhodius ad Scribon. Largum. p. 44 sq. 



J. Alb. Fabricius, De Hominibus ortu non differ entibus. Opuscul. p. 441. 



Ch. Collignon, Miscellaneous Works. Cambridge. 1786. 4to. p. 25 sq. 



§ Consult J. Haygarth, Med. Obs. and Inquiries, vol. iv. p. 198 sq. 



|| The existence of a fourth bone (called Lenticular), commonly admitted 

 since the time of Franc. Sylvius, I have disproved at length in my Osteology. 

 p. 155 sq. edit. 2. It is wanting in the greater number of perfect examples 

 from adults. 



M 2 



