Royal Society* 431 
Stapes^ to which it is conne£led, by means of the Os lenticularet 
and fo removes a httle the internal and lateral part of the bafis 
of this Imall bone from the internal and lateral part of the Fe- 
neftra Labyrinthi j between both which there is formed a fmall 
Rimula , which affords a paflage into the Concha for the aethereal 
naatter that comes loaded, as it were, with the impreflions re- 
ceived from fonorous bodies, and that is about to enter into the la- 
byrinth : From what has been faid, it plainly appears that both 
the tendons of the monogaftric mufcle of the ear are defigned 
for the fame ules^ altho* their motions, as being in different di- 
redions, are differently performed, fb as to refill each other, as 
may be leen from what is faid above 5 and indeed each of them 
in a peculiar manner ftretches the exterior membrane of the 
tympanum, and endeavours to make it plane 5 by which means it 
gives a more ready accefs to the aethereal matter into the cavity 
of the Tympanum^ that carries along with it the impreflions of 
fonorous bodies j whilft the longer tendon opens a little the fupe- 
rior part of the Fenefira Lahyrinthi^ the fhorter one does a 
little open the lateral and internal part of the fame Feneftra^ fb 
that the chink made by this means admits fbme portion of the 
xthereal matter into the Concha : The lefler mufcle of the inter- 
nal ear, if confidered with regard to its rife and infertion, cannot 
contra(S itfelf, but at the fame time it mufl draw the head of the 
StapeSy in which it is inferted, from the external towards the in- 
ternal parts of the Tympanum, and fo open a little the lateral and 
external part of the Fenefira of the labyrinth, to give admifTion 
to the setnereal matter into the Concha : From this it very plainly 
appears, that this lefler mufcle of the ear, whilfl it contracts 
itlelf, and the monogaflric mufcle, confidered as a6iing by its 
fhorter tendon, open the Fenefira Labyrinthi in a quite 
different manner; and hence^-doubtlefs it is, that by reafon 
of thefe natural oppofite motions of both thefe mufcles, the 
Fenefira Labyrinthi never opens but a little, and that only 
on its external fide by the aaion of the lefier mulcle: On the 
contrary this Fenefira is open in its fuperior parts, and at 
the lame time on its internal fide, where the monogaflric mufcle 
contra(!:ls itielf, as has been fully and plainly ihewn above: 
That the parts already defcribed, with which the cavity of the 
Tympanum is furniflied, naturally ferve for the ufes afligned them, 
i!''^/>^^6";; J thinks cannot be called in queftion ; fince the fcnle of 
hearing is impaired as often as their natural ftate is changed ; yet 
he would not have any one think, that thele parts are ablolutely iie- 
cefTary to that lenfe ; becaufe he has oblerved more than once, ia 
dif. 
