{666) 
the paffage of his left Ear was quite fhut up, and that of the 
right Ear proper tionally diftended, and too open. This Gentle- 
man being, for fome time recommended to my Care, amongft 
other things, I fpent fome thoughts in fearching the caufe of his 
Deafnefs in the Ear, whofe pafTIige was open. And having found 
that the Auditory Nerve was not perifhed , but that he could 
hear the found of a Lute- firings holding one end thereof in his 
Teeth? and had fome perception of any very vehement found, 
I fuppofed the defe<& to lie in the want of due Tenfion of the 
Tympanum of his Ear^ whofe Ufe I took to be, onely to pre- 
ferve the Auditory Nerve, and Brain, and inward parts of the 
Ear from outward injury by cold, Duft ; &c. and to be no more 
to Hearing, than glafs in the window is in a Room to feeing, i.e. 
as the one intromits Light without Cold or offence to thofe in 
the room, fo the other permits Sound to pafs 5 and (huts out 
what elfe might offend the Organ ; as appears in the Experiment 
of breaking the Tympanum of a Dog, who hears never the worfe 
for lome few weeks, till other caufes/as Cold^ &c. vitiate the 
Organ. 
But for the Free paffage of the Sound into the Ear, it is requi- 
lite j that the Tympanum be tenfe and hard ftretched $ otherwife 
the laxnefs of that membrane will certainly dead and damp the 
Sg^dd. And 'becaufe the Tympanum is fixed in the circumfe- 
rence "thereof to the Annulus 0/^0^ and fo is not capable of Ten- 
fion that way,in fuch manner as a Drum is braced $ there remains 
another way ; by drawing it at the Center into a Conoid term. 
And that is the principal office of the 3. o fides , viz. the Mal- 
leus, Incus ^ and Stapes 5 whereof the Stapes is fixt to the inner 
Bone, and part of the Malleus y to the Tympanum^ and the In- 
cus between them joynd on [one part to the Malleus , and on 
the other to the Stapes by Ginglymoide Joynts, fuch as in which 
t he upper and lower double Teeth meet one another. And by the 
help of a Mufele. drawing the Incus, thefe three bones, which 
otherwife could lye more ftreight, are brought to a Curved or 
Arched pofture • and the Stapes being fixt unmoveable, the Mal- 
'leus yields, to, bring the terms of that line nearer^ in proportion 
as it is 'curved., and draws the Center of the Tympanum, ftretching 
the furface of it from a Plain to a Conoid figure, within the fame 
Cir- 
