'4<5 The Anatomy of a HOVkS^. Chap. IV. 



may the better contribute to Hearing ; and ftrong, that it 

 may the better endure loud Sounds, or any other external 

 Injuries ; for if once this be broke, or any way relax'd, a 

 Deafnefs mull unavoidably enfue. 



77 Concha Within this Membrane there is a Cavity 



nxjith ihi fmall ^"^^^ ^he CoHcbay wherein are four little 

 Bones contaimJ Bones, which are .bound together by a fmall 

 in it. Ligament proceeding from the Cord of the 



Drum : The firft is called the Hammer, 

 which lies upon the fecond, called the Anvil. The third 

 is named the StapeSy or Stifrop ; but in a Horfe it is trian- 

 gular, like the Greei Letter A. Upon the upper Part of 

 the Stirrop, the longed Foot of the Anvil ftands. The 

 fourth is called Orbicular^ it is of a round Shape, and tied 

 with a flender Ligament to the Side of the Stirrop, where 

 it is fattened to the Anvil. 



_~ . ... Thefe Bones are a Defence to the Drurn, 



ty^- ^j^(j preferve it from being torn, or beat 



inwards by the violent Vibrations of the outward Air in 

 loud Sounds, and are thus aflifting to the Senfe of Hear- 

 ing : When the external Air beats upon the Drum^ it is 

 driven againft the Hammer, Avhich ftrikes upon the Anvil, 

 as the Anvil beats againft the Stirrop ; and as this Force is 

 more or lefs exerted, fo the Stirrop opens the oval Wm- 

 dow mcMre or lefs, and proportionably the Sound apjiears 

 louder or lower. 



fj.. ^ , The Cavities within the Os petrofurn are 



Jbe L,oncna. j^^ Number three : The tirft, wherein thefe 

 four little Bones are iituated, is called \\-\t Concha., from its 

 refembling the Shell of a Tabor. When the Membrane is 

 ftruck upon by any outward Sound, the Eccho is made in 

 this Cavity, as in a common Drum. 



There are in this Cavity divers Inftruments, whereof 

 fome are fpr Pulfation, as the four little Bones above-men- 

 tion'd ; fome are for conducting the Air into llie other Ca- 

 vities, fuch are the two fmall Perforations, called the IVin- 

 doivs ; and a third fort are thofe by which the pituitous 

 Matter, colle<5led within this Cavity, is dilcliarged towards 

 the Palate and Nofe. 



7he o'valWin- ^^^ ^^^ of thefe two Perforations, being 

 jgr^^ the uppermoft and lajgeft, is from its Figure 



iTam'd the cval JViJidow, which is kept fhut 

 next the Concha, by the Bafis of the Stirrop, as often as 

 the Sound ceafes. The other, which is round, is always 



open. 



