Royal Society. 433 
ervals of time, yet VieuJJeris luppofes it certain, both from the 
period of time, for inftance, between the firft and lecond vibra- 
tion, and from its gentle extenfions, that the faid mufcle is deter- 
mined to a contraction, with that elafticity it acquired whillt 
extended 5 and that it is a6lually contracted, by means of the ani- 
mal fpirits, which hadjuft entered the pores of its fibres: The 
contraction of the monogaftric mufcle draws the Stapes from the 
internal towards the external parts of the ^ympanumy and thus 
extending the lefTer mulcle of the internal ear, dilpoles it in fuch 
a manner, as that it acquires an elafticity, by which it is firted and 
determined to contract itlelf ; and as loon as the monogaftric muf- 
cle is again extended, in the manner juft now explained, it is 
actually contracted by means of the animal fpirits. 
Vieujjens comes next to confide r the internal and external parts 
of the labyrinth- and he gives an account of the bone, which con- 
ititutes the internal \Parietes of each of its cavities, and which 
he fays is white, very hard, and compaCt 3 it feems to be formed 
thus by nature, that when the ethereal matter, charged with the 
impreilions of fonorous bodies, ftrikes upon the faid \ParieteSy 
it may lofe little or nothing of its motion, but communicate it, 
the fame or nearly lb, to the animal fpirits contained within the 
ramifications of the 'Portio Mollis of the ear, which are vari- 
oufly Ipread on the internal parts of the labyrinth, as will after- 
wards be fhewn : In the external parts of the labyrinth, there 
are only three things obfervablej viz. a bony partition which 
poflefles its luperior part, and by which its three femi-circular 
duCtvS are leparatcd from each other, together with two apertures 
tiot far from one another, by which the aethereal matter is con- 
veyed from the cavity of the Tympanum into the labyrinth 5 this 
portion of the Os Petrofim,^ has this in peculiar, that its inter- 
nal texture is cellular, in which a great number of capillary blood- 
veflels are diffemmated, and the gentle heat of the blood con- 
veyed in thefe vefTels, cheriflies and prcferves the natural motion 
of the animal fpirits, lodged in the pores of the fmall nervous 
membranes within the lemi-circular duCts of the labyrinth, and 
fo prevents their being too much condenfed, and becoming unfit 
for the purpofes of hearing: The two apertures above-mentioned 
are in that part of the Os Petrofum^ which conftitutes the bafis 
of the labyrinth j the firft is of an oval figure, and fituated a 
little higher than the fecond, VieuJJens thinks this fhould be 
called the Fenejlra of the labyrinth, becaule it opens into the 
ConcJoa, and confequently into the more internal parts of the la- 
byrinth 3 the bafis of the Stapes is applied to this Fsnefira and 
Vol. III. I i i ihuts 
