4^8 ME M O I R S of the 
nifhed, on account of the flux of the blood fomewhat impeded? 
if at that time it happen to be dilated with a very hot and dry 
vapour, fo as ftrongly to refle£l the pulfations; in that cale it agi- 
tates both the ambient air, and that included in its cavities in 
fuch a manner, as to yield the very lame, or nearly the fame vi- 
brations with thofe produced by the fmall and quick reiterated 
ftrokes of a filver hammer, upon an anvil of filver, or fome luch 
fonorous metal, and which for that reafon is apt to caufe a ftrong 
re-percuflion ; hence it is no wonder, that fuch vibrations, when 
they reach the Centrum Ovale of the brain, excite in the mind 
an idea, which reprefents a preternatural noiie commonly called 
Tinnitus: VieuffenSy on frequent examination, never obferved 
more than cwo mufcles of the internal ear, which receive almoft 
imperceptible nerves from the fifth pair, and are furniflied with 
very fmall blood- vefTels, which are ramifications of the carotid 
artery and jugular vein 5 the firfl of thefe mulcles is thicker and 
longer than the other, having two heads and two tendons or tails, 
but one belly, which therefore he calls the monogaftric muiclej 
the firfl head is covered with a membranous coat, and arifes from 
a little bony Sinus above the fuperior part of the aquxduft^ the 
fecond head, which appears altogether fleihy, takes its rile not 
far from the external fide of the above bony Sinus y the fle/liy 
fibres that compofe thefe two heads are very clofely united a little 
before they enter the cavity of the Tympanum^ and then they ter- 
minate in one belly, enveloped with a ftrong membranous coat ^ 
after which, thefe flefhy fibres, extending themfelves towards the 
cavity of the Tympanum^ a little after they have entered it, are 
again leparated, and become two tendons enveloped in a ftrong 
membranous coat: The firft of thefe is longer and more flender 
than the fecond, and after raifing itfelf a little upwards, by means 
of a fmall membranous pulley, it is conne6led to that part of the 
Os ^etrcfumy where the aquaedufl of Fallopius begins, or that 
bony canal, which receives the ^ortio Dura of the ear; {q that 
by the help of this membranous pulley, it performs all its mo- 
tions freely j this tendon bending downwards, defcends perpendi- 
cularly upon the flender Apphyfis of the Malleus^ and by ex- 
panding itlelf a little, is conneiSted therewith, hence it happens 
that its connection extends as far as the neck of the Malleus : The 
fecond tendon of this mufcle is fhorter, and thicker than the firft, 
and covered with a pretty thick membranous coat, extends almoft 
in a ftreight line to the cavity of the Tympanum^ and is fafteiied 
to the middle part of the head of the Malleus^ and is {o expanded, 
as to reach the body of the Incus^ and thus it ferves for connect- 
ing 
