( 262 ) 
. The exter0a!^^^rcolle£bs the founds J and augments the 
ioiprtijioriby the various refledions the voice undergoes 
in its paffage through the folds of it* The ufe of the Mufcles 
he acknowleges to beobfcure , though he gueffes their 
action ttiay be to contraft , or dilate the Concha as the trem- 
blings pf the are ftrong, or weak. 
jIn the Internal Ear, the Tympanum is ftretched and made 
flack again , by the mufcles of the Malleus , in the tenfion 
of it both the Mufcles ad> but in the relaxation onely the 
external , whofe action it is to reduce it from z Concave to 
^Plam^ all which is manifeft from the infer tion of the 
4/«/ir/^/ ; the determination of which aftion he deduces, 
not from the will , but from the various difpofiiions, and 
appulfe of the ObjeHs^ as a lharp note is caufed by a body 
whofe parts are fo difpofed as to be capable of very quick 
Vibrations^ which they as fuddainly imprefs onthe Air^ 
on the contrary 3 the flat note proceeds from the Jlower 
Streaks of a body with parts that can onely be fo agitated , 
to which differences the Tympanum readily complies, and 
does as it were put on their particular CharaBer y this is 
delivered hence to the Malleus^ and fo forward, till at laft 
the fame flu ftuation is caufed in the Os Petrofum^^nd in the 
y Labyrinth* 
The ^quiduB ferves chiefly for the ingrefs and egrefs 
of Airy to and from the Cavity into which it opens, and not 
to fupply the defefl: of tht Tympanums which' he argues 
fiom a deaf mans hearing the found of an Injlrument^ then, 
and then onely when he holds the A^^t^^ of it between his 
Teeth, 
The immediate Organ of hearing he perfwades to be 
the thrct Semt'Circular Canals y they being found in all -^» 
nimalszud in fome onely they ; as in Birds^ and Fijhes. 
From the Communication of the harder portion of the 
Juditory Nerve with the branches of the Fifth Pair^ which 
are diftributed to t\iQ Organs ohh^f^oice ^ proceeds that 
