53 8 ANATOMY. 
the horizontal limb is made hollow by the lateral finufes 
inclofed in the tranfverfe procefs of the dura mater; the 
fofla in the right tide being generally a continuation of the 
one made by the longitudinal (inns in the perpendicular 
limb, and therefore is larger than the left one. The in¬ 
ner furface of the cuneiform apophyfe is made concave 
for the reception of the medulla oblongata, and of the ba- 
filar artery. A furrow is made on each tide, near the 
edges of this procefs, by a ftnus of the dura mater, which 
empties itfelf into the lateral finus. 
The holes of this bone are commonly five proper, and 
two common. The firft of the proper holes, called fora¬ 
men magnum from its fize, is immediately behind the wedge¬ 
like procefs ; and allows a paflage to the medulla oblonga¬ 
ta, nervi accefforiL, to the vertebral arteries, and fome- 
limes to the vertebral veins. At each fide of this great 
bole, near its fore part, and immediately above the con¬ 
dyles, we always find a hole, fometimes two, which foon 
unite again into one, that opens externally ; through thefe 
the ninth pair of nerves go out of the fkull. The fourth 
and fifth holes pierce from behind the condyle of each fide 
into the fofla; of the lateral finufes; theyferve for the 
paifage of the cervical veins to thefe finufes. Often one 
of thefe holes is wanting, fometimesboth, when the veins 
pafs through the great foramen. The two common fora¬ 
mina are the large irregular holes, one in each fide, be¬ 
tween the (ides of the cuneiform procefs and the edges of 
the petrous bones. 
The occipital bone is among the thickefl of the cranium, 
though unequally fo; for it is ft ranger above, where it 
has no other defence than the common teguments, than it 
is below; for, being there prelfed by the lobes of the brain 
and cerebellum on one fide, and by theadlionof the nruf- 
cles on the other, it is fo very thin as to be diaphanous in 
many Ikulls: but then thefe mufcles ward off injuries; 
and the ridges and fpines, which are frequent here, make 
it fufficiently flrong to refill ordinary forces. The tables 
and diploe are tolerably diftincl in this bone, except where 
it is fo thin as to become diaphanous. 
The occipital bone is joined, above to the offa parietalia, 
and to the triquetra, when prefent, by the lambdoid fu¬ 
ture; laterally to the temporal bones, by the additamenta 
of the lambdoid future; below to the fphenoid bone, by 
the end of its cuneiform procefs, in the fame way thatepi- 
nhyfes and their bones are joined. For in children a liga¬ 
mentous cartilage is interpofed between the occipital and 
iphenoid bones, which gradually turns thinner as each of 
the bones advances, till their fibres at laft run into each 
other ; and, about fixteen or eighteen years of age, the 
union of thefe two bones becomes fo intimate, that a fe- 
paration cannot be made without violence. The os occi- 
pitis is joined by a double articulation to the firft vertebra 
of the neck, each condyle being received into a fuperior 
oblique procefs of that vertebra. 
Os etkmoides, or the fuve-like bone, has its name from 
the great number of fmall holes with which it is pierced. 
Its l'everal parts are, the cribriform lamella with its procefs, 
the nafal lamella, cellules, and effa fponginofa. The thin ho¬ 
rizontal lamella is pierced obliquely by a great number of 
fmall holes, through which the filaments of the olfaftory 
nerves pafs. In a recent fubjeft, thefe holes are fo clofely 
lined by the dura mater, that they are much lefsconfpicu- 
ous than in the Ikeleton. ‘ From the middle of the internal 
fide of this plate, a thick procefs rifes upwards; and, be¬ 
ing higheft at the fore-part, gradually becomes lower as it 
is extended backwards. From fome relemblance which 
this procefs w as imagined to have to a cock’s comb, it has 
been called crija galti. The falx is connected to its ridge, 
and to the unperforated part of the cribriform plate. When 
the crifta is broke, its bafe is fometimes found to be hol¬ 
low, with its cavity opening into the nofe. 
From the middle of the outer furface of the cribriform 
lamella, a thin folid plate is extended downwards and for¬ 
wards, having the fame common bafe with the crifta galli. 
Generally it is not exactly perpendicular, but is inclined 
to one fide or other, and therefore divides the cavity o-f the 
nofe unequally. Its inclination to one fide, and flexure in 
the middle, is fometimes fo great, that it fills up a large 
fltare of one of the noftrils, and has been miftaken for°a 
polypus there. At a little diftance from each fide of this 
external procefs, a cellular and fpongy bony' fubftance 
depends from the cribriform plate. The number and fi¬ 
gure of the cells in this irregular procefs, are very uncer¬ 
tain ; but they open into each other, and into the cavity of 
the nofe : the upper mo ft, which are below the aperture 
of the frontal finufes, are formed like .funnels. The outer 
furface of thefe cells is fmooth and plain, where this bone 
aIMs in compofing the orbit; at which place, on each fide, 
it has the name of os planum. Below the cells of each 
fide, a thin plate is extended inwards; and then, bending 
down, it becomes thick and of a fpongy texture. This 
fpongy part is triangular, with a ftraight upper edge placed 
horizontally, an anterior one flanting from above, down¬ 
wards and forwards, and with a pendulous convex one 
below. The fide of this pendulous fpongy part next to 
the feptum narium is convex, and its external fide is con¬ 
cave. Thefe tw’o precedes of the ethmoid bone have the 
name of ofja fpovgiofa, or turbinata fuperior a, from their 
fubftance, figure, and fituation. All the prominences, 
cavities, and meanders, of this ethmoid bone, are covered 
with a continuation of the membrane of the noftrils in a 
recent fubjecl. The cellular part of each palate-bone is 
contiguous to each os planum, and to the cells backwards. 
The lower edge of the nafal perpendicular plate is received 
into the furrow of the vomer. Its pofterior edge is joined 
to the fore-part of the proceffus azygos of the fphenoid: 
bone. Its upper edge joins the nafal procefs of the frontal 
and nafal bones; and its anterior one is connected to the 
middle cartilage of the nofe. 
The ufes of this bone are to fuftain the anterior lobes of 
the brain ; to give paifage to the olfactory nerves, and' 
attachment to the falx ; to enlarge the organ of fmelling, 
by allowing the membrane of the nofe a great extent, to 
ftraighten the paflage of the air through the nofe, by 
leaving only a narrow winding canal, on the (enfible mem¬ 
branous fides of which the fubftances conveyed along with 
the air muft ftrike ; to form part of the orbit of the eyes 
and feptum narium; while all its parts are fo light as rot 
to be in hazard of Separating by their weight; and they 
are fo thin as to form a large furface, without occupying 
much fpace. This brittle fubftance, however, is fuffi¬ 
ciently protected from external injuries by the firm bones 
which cover it. If this bone is feized on by any corroding 
matter, we may eafily conceive what deftruction may enfue. 
Hence it is, that an ozaena is difficult to cure ; and that in 
violent feurvies, or in the lues venerea, the fabric of the 
nofe, the eyes, and even the life itfelf, are in danger. The 
fituation of the nafal plate may lhew us how dangerous at 
fradlure of the bones of the nofe may be, when made by a 
force applied to their middle fore-part, of a perfon in 
whom this nafal plate is perpendicular. 
Os fpkenoides, or wedge-like bone, has two or three re¬ 
markable precedes from each fide of it, which arc all of 
them again fubdivided. The firft pair is the tv/o large 
lateral precedes or wings; the upper part of each of which 
is called the temporal procefs, becaufe they join tire temporal 
bones. That part of the wings which juts out towards 
the infide, fomewhat lower than the temporal apophyfes^ 
where it makes up part of the orbit, is thence named orbitar 
procejfes. Behind the edge feparating thefe two precedes, 
there is often a fmall groove, made by a branch of the fu- 
perior maxillary nerve, in its paflage to the temporal muf- 
cle. The lowed; and back part of each wing, which runs 
out (harp to meet the ofiapetrofa, has been f iled the fpinous 
procefs : from near the point of which a (harp-pointed 
procefs is frequently produced downwards, commonly cal¬ 
led fylform,- that affords origin to the ptery-ftaphylinus 
externus mufcle. From this ftyloid procefs a very fmall 
groove is extended along the edge of the bone to the hol¬ 
low at the root of the internal piate of the following pro- 
ceflesj 
