ee 
an is covered he sae | by a mucous lining, 
which, ere. the tranfition from the comm 
ae the pituitary Genre. is foft 
ry diltin@ cuticle, and numerous ftrong irate which are 
nein: long enough to project at the open 
Il. Cavities of tis a les? —For their r genera figure, the 
bones compoling t c. fee CRANIU 
The nottrils are parted from the cranium by the cribri- 
form plate of the ethmoid; the palatine portions of the 
mY raulary nd palate bones form the inferior bound- 
y ey are parted from 7 e mout 
otbital oe a the ethmoid and the 
towards the orbit ; and they extend eee to the projec- 
Hah the cheek, under the eyes, if we include the maxillary 
inu 
' Their — is nearly horizontal, from the ee red 
which they commence in the ‘heir 
“Tittle 
a 
+) 
“ 
“ 
5 
aa 
he offa nafi, in the middle, of the cribri- 
form plate of the ethmoid, and behind, of the body of the 
{phenoid. The offa nafi flant downwards and forwards from 
the front of the ethmoid, and the {phenoid downwards and 
backwards from the back of the fame bone. Hence the 
is in the 
_ les it diminifhes upwards on account of the curved 
o muc 
he tranfverfe mea(arementl is greateft a and becomes 
fmaller as we afcend: the fuperior concha 
be apparent from the fact, 
brane in cold very often entirely obftrués the paflage of 
air through it. 
IIT. ‘lhe opening of the noftrils behind into the set ae 
al eae immediately under the bafis cranii, and over the 
an palati. There are two nearly oval apertures, ou 
an = in a ee half an inch poet feparated by the 
In front it 
ps the fkin, and behind with the acu eae of lie 
unguis clofe them behin 
If we begin to trace it from the floor of the nofe, we fee 
it atvending along the feptum to the roof of the cavity, 
orming no fold in its courfe, and eafily detached from the 
one a cartilage that compofe the feptum. It is con- 
tinued on the under furface of the cribriform plate, of 
aera it clofes the foramina: in front it paffes to the back 
of the offa nafi, and behind to the under furface of the 
ae hesid: entering and lining the cells of that bone, ere 
times sea ie in g their orifice, fometimes leaving it as wi 
as in the 
e pi aay membrane is then continued over the ex- 
cera furface of the noftril, firft alga i flat plate of 
the ethmoid and the {uperior co ncha, and then reflected at, 
the convex edge of the i 
_ 
& 
Li ve 
a 
pofterior en 
ge aba baa which the pituitary receives veffels 
and n embrane lines the echmoid 
cells, coe covers ie middle concha, is Prhecied at its in- 
ferior edge, and thus enters the middle meatus, which it 
lines. It is prolonged through an opening, generally very 
maxillary finus, which it lines. The 
entry to the finus is near the front of the meatus; and 
the aperture leads into the upper and anterior part of 
the ¢ cavity. After removing the middle concha, a bony 
plate is expofed, covered by the pituitary membrane, and 
terminating above by an unattached oe this plate con- 
ceals the narrow entrance of the fi The large opening 
of this cavity in the feparate ace one is diminifhe 
by the appofition of the furrounding bones ; but it is ftill 
farther contracted by the membrane, of which there are two 
layers . this part; one taloaatig to the nofe, the other to 
the finu yt hee entrance of ie maxillary finus there 
is an pet rture, b the membrane paffes into the ante- 
rior ethmoidal calle ad the frontal finus, without forming 
he middle — the membrane is continued over 
h ng a very thick and large fold at 
its margin, by _ ie apparent depth of the concha is 
the edge of the inferior concha the 
are inferior meatus, lines it, is con-~ 
e ductus nafalis, and 
noftrils are continuous with each other. 
fide of the opening it forms a more or lefs diftin& perpen- 
dicular fold ; behind which, juft where the nofe and pharynx 
join, it covers the rd of the Euftachian tube, forming 
above it a deep cul d 
The pituitary or yer is analogous to other 
mucous membranes in the fluid, which it produces, but differs 
from them in its thicknefa, which is much more confiderable. 
parts ard fubjects. rous layer, whic 
periofteum or perichondrinm of the nafal cavities, is joined. 
to a mucous ftratum, in order to form the pituitary mem- 
brane, which muft confequenty be clafled among. the fibro- 
mucous organs. This apart re may be very eafily fhewn 
by breaking the feptum, and removing the avuene4 the. 
fibrous portion is ae ie becaufe it adheres lefs firmly 
