Royal Society, 427 
plainly appears, that a tumultuary fort of motion, producing a 
preternatural found is neceflarily excited within the -lympanum^ as 
often as there is tranirnitted into the veffels of this membrane too 
great a quantity of much rarilicd and vaporous blood, arifing from 
lurfeits, ob(tru6tiorts in the lower belly, long and painful flu- 
<3y, ^c. which blood, from its too great quantity and rarefaction 
gives too high a pulie and dilates too much the fmall arreries in 
which it is conveyed 3 by which and a plentiful emiflion of va- 
pours, it llrikes lo upon this membrane, as to occaliDn a certain 
confufed tumultuary noile within the 'tympanum ^ eipecially, if by 
realbn of an obltru&on in the aquasduil, or the too clofe texture 
of the exterior membrane of the "jtympanum^ thcle vapours can- 
not eafily perfpire: The impreffion of this noile tranirnitted to 
the Centrum Ovale of the brain, excites m the mind an idea, 
which IS commonly called a noife in the ear 3 of which there are 
three ibrts ; viz, "Bomhus a humming, Sibilus a hiding, and 'Tin- 
nitus a tingling noife : When the vapours that occafion a mur- 
muring nolle in the ears, being too plentiful, and agitated too 
much, are io moift, as to approach pretty near to the nature of 
water, they relax the interior membrane of the ^Cympanum^ and 
being eafily moveable, they bend and turn it every way 5 hence it 
happens, that this membrane being ibmewhat relaxed and bent by 
the various and undulatory motion communicated thereto, agitates 
in fuch a manner not only the circumambient air, but likewilc 
that contained within its cavities, as to have proper vibrations in 
a flow luccefTive manner communicated thereto : Thefe vibrations 
by means of the animal Ipirits, contained in the 'Port to Mollis 
of the ear, are conveyed to the Centrum Ovale of the brain, and 
excite in the mind that idea, which repi^ients that confufed noile, 
commonly called Bombus-. YVhen the vapour that excites a noife 
in the ears is lb dcftitute of watry particks, as to be of the na- 
ture of a dry exhalation, rather than a mere vapour, and lo be- 
comes flatulent 3 this linking againft the interior membrane of the 
Tympanum in fome mealure dries and expands it 3 hence it is 
that this membrane exates ftrong vibrations, which are indeed 
fuccefTive, but very quick, and move in Ifreight lines or nearly lb 5 
and that fuch vibrations are alrnoll like thole produced by a mere 
Flatus y thcle likewife, tranlmitted to the Centrum Ovale of the 
brain, in the manner above explained, excite in the mind an idea 
that reprelents a tumultuary fharp lound, commonly called *S/- 
hilus : When the interior membrane of the 'lympanumy or any 
part thereof, has frequent and ftrong pulles, which quickly 
liicceed each other, from the fmall arteries with which it is fur- 
H h h i niflu'd, 
