Royal Society. 407 
then expands itfelf into two fmall membranes 5 one of which 
lines the internal fuperficies of the cavity of the fuperior femi- 
circalar du6t, and the other the internal fuperficics of the cavity 
of the inferior fcmicircular du6l : The inferior, and fmalleft 
ramification oUhe'PomoAfollis of the feventh pair, upon fending 
forth one or two, almoll imperceptible fibrils, which are fpread 
on that internal part of the Os ^etrofim, wherein the lemi- 
circular du6ls of the labyrinth are excavated, enters a very fmall 
Foramen, by means of which it infinuates it{e\{ into the lowed 
part of the Concha, and fpreading itfelf therein, it is fpent in 
forming that thin membrane, which as has been /l:iewn above 
lines the interior fuperficies of the Concha, excepting a fmall 
portion thereof, which enters the middle of the lemi-circular 
dufl, thro' a Foramen fituated a little below the Torta Commu- 
nis, and there it is expanded into a very thin fmall membrane* 
which lines the internal fuperficies of that dufl: The fine and 
fmall nervous membranes in the internal parts of the femi-cir- 
cular dufts of the labyrinth are furnifhed with exceeding fmall 
blood- veflels, for the mod part imperceptible 3 efpecially, when 
they contam little or no blood 5 the membranes themfelves as 
being furnifhed with a very limpid and fubtile fpirituous 
liquor, particularly in new-born children, are fo fofr, as hardly 
to bear touching 5 befides, whenexpofed to the fun, they quickly 
dry up, and become £0 friable, that if moved out of their 
place, they crumble away, and are reduced into an impalpable 
powdery in like manner, that limpid fpirituous liquor with 
which thefe membranes are always furni/hed, and which 
feems to be no other than the animal fpirits fomewhat conden 
i^^, by reafonofthe native coldnefs of the place, is diffipated 
m a moment, as foon as the femi-circular dufts of the labyrinth 
are laid open, which in new-born children Vieulfens always 
obfervedto be repleni/hed with this liquor 3 but the cafe would 
neceflarily be otherwife, were not the five orifices of the femi- 
circular dufts of the labyrinth, which open into the internal 
parts of the Concha, naturally clofed up by the nervous mem 
brane above defcribed; yet Vieujfens does not at all doubf 
but that this liquor gradually and mfenfibly infinuates itfelf 
into the pores of the nervous membrane of the Concha, and pre- 
vents Its being too much dried up 3 and hence it is, thatit pre- 
ferves its native temperament, by which it contributes to the 
fenfe of hearing. 
The middle ramification of the Tortio Mollis of the feventh 
pair of nerves fends forth, near that part of the Os "Petroftm, 
which 
