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by a ligament. The motion permitted at the joint between
the head of the rib and the border of each of the vertebræ
next above and below it is not extensive; but it is sufficient
to give the body of each rib, which has the relation of a long
lever to the joint as a fulcrum, a wide sweep outwards and
upwards in the act of deep inspiration. Proceeding onwards
from the head, and passing over the neck, which is the
smallest and roundest part of the rib, the next object is the
tubercle, an elevation on the posterior surface, by which the
rib is articulated with the end of the transverse process of
the vertebra next below it. Farther outward is the angle,
an oblique projecting line at which each rib turns somewhat
more upwards and becomes flatter. The remainder of the
rib is its shaft. This is thin and flat; its surfaces are both
nearly smooth, the outer being slightly convex, the inner as
slightly concave; the upper edge is rounded; the lower
(which is also directed somewhat outwards) is sharp, and,
from the angle inwards, is grooved on its inner aspect, where
the intercostal vessels and nerves lie. The end of the
osseous part of each rib has a rough surface, to which is
adapted one end of the costal cartilage, of which the other
end (except in the instances already mentioned) is attached
to the sternum. The costal cartilages have each the same
general form and direction as the part of the rib to which
they are appended; they may be regarded as mere prolonga-
tions of the ribs, the purpose of their being cartilaginous
instead of bony being that of giving more elasticity to the
walls of the chest. Each of them, except the first, is arti-
culated with a slight capacity of motion to a depression on
the border of the sternum.

The direction of the body of the rib is first downwards
and backwards, forming an arc of a small circle, to the
angle, at or near which it seems twisted on itself, and then
sweeps round forwards and a little upwards in the arc of a
larger circle. The distance from the head to the part at
which this change of direction takes place, is greater in the
lower than in the upper ribs, and in the same progression is
gradually increased the obliquity of the ascent of the carti-
lages towards the sternum. The length of the ribs and
their cartilages together becomes regularly greater from
the first, that is, the uppermost, to the seventh or eighth,
the rest become gradually shorter, especially in their os-
seous parts.

Some of the ribs have particular characters in which they deviate from the general description. The heads of the first, eleventh, and twelfth, have but one articular surface, being each connected with but one vertebra; the first and twelfth have no angles, the second and eleventh scarcely any. The first forms nearly the half of a circle of a very small radius compared with those of the ribs below it; its surfaces are horizontal; the upper is marked by two grooves over which the subclavian artery and vein pass, and by an impression between them to which the anterior scalenus muscle is attached; the lower surface has no groove; the sternal end is very broad; the head is small. The second rib presents characters intermediate between those of the first and those of the true ribs below it.

The Sternum, or breast bone, is single only in the adult; in youth it is composed of at least two pieces (of which the upper (Fig. 7, A) is named manubrium), and in the fœtus of many more. Considered as one bone, its form is elongated, broader and thicker above than below, where it, terminates in

Fig. 7*.

Ꭺ

B

a long narrow process, which is generally cartilaginous, and is named the ensiform or xiphoid cartilage (B). The anterior surface of the sternum is marked by four transverse lines (3, 4, 5, 6) which indicate the divisions between the five principal parts of which it is composed. These marks are repeated on the posterior surface. Along its borders there are (proceeding from above downwards), first, at each of the angles between its upper and lateral edges, a shallow depression (1) into which the extremity of the clavicle is received; then immediately below this an oval depressed surface (2) to which the cartilage of the first rib is fixed; and lastly, along each side six other similar surfaces separated by notches with which the cartilages of the six following ribs articulate. Of these six, the four upper are placed at the ends of the transverse lines; so that each of these ribs articulates at its sternal end with two pieces of the sternum, just as, at its other extremity, it articulates with two ver

tebræ.

The general structure of the chest, and its adaptation to the movements of breathing, the most important function in which it is particularly engaged, are described in the article RESPIRATION.

The Bones of the Skull are divided into two chief sets,
Fig. 8.

those of the Cranium, or case for the brain, and those of the Face. They are represented in the annexed sketches separated, yet in their natural relative positions, in three different aspects: in Fig. 8, as seen from the front; in Fig. 9, as seen in profile; in Fig. 10, as seen when, after removing the top of the skull, one looks from above upon the bottom of its interior

Fig. 9.

on either side of it are fixed parts of the upper jaw, and in the middle the nasal bones, which rest behind on a process called the nasal spine (3). At the outer extremity of each orbital arch is the external angular process (4, 4), and at the inner extremity the internal angular process (5, 5); the former is articulated with the malar, the latter with the upper jaw and lacry mal bones. Near the internal process is the Supra-orbital Foramen or notch (6, 6), through which the frontal vessels and nerve pass from the orbit to the forehead. Just above it and by its side is a rounded elevation, the frontal protuberance (7), which marks the situation of the subjacent frontal sinuses, air-cavities, between the two layers of which the bone is composed. They vary much in size in different persons, and communicate with the interior of the nose. On either side of the middle line, and extending above the orbital ridge, the surface of the bone is again elevated in the superciliary ridge (8, 8), an arched prominence behind the eyebrow. The rest of this anterior surface is smooth and even, but in different persons its form is as varied as that of any other feature. On either side it terminates rather abruptly with a curved border (9), which forms the front boundary of the Temporal fossa (10), and behind which there is a smooth surface, to which the fore part of the temporal muscle is attached.

Fig. 11.

Fig. 10.

a

The posterior or cerebral surface of the Frontal bone (Fig.
11, b) is concave. Along the middle line there is a broad
groove (1), in which a part of the longitudinal sinus [BRAIN]
lies; and at the fore and lower end of this a ridge, to which
a process of dura mater called the falx is attached.
ridge ends at a hole named the Foramen cæcum. The rest
of this surface is marked by depressions and ridges fitting
to the convolutions of the surface of the brain.

The

The orbital portions (b, 3, 3,) of the frontal bone are thin plates extending almost horizontally backwards from the orbital arches. Between their inner borders is a space, the The Bones of the Cranium are, the Frontal (a), the two ethmoid notch, into which the ethmoid bone fits, and just Parietal (b), the two Temporal (c), the Occipital (d), the anterior to which are the apertures (4, 4) leading into the Sphenoid (e), the Ethmoid (f); those of the face are, the frontal sinuses. The under surface of each plate is contwo Nasal (g), the two superior Maxillary, or upper Jaw- cave, smooth, and even; and has at its outer and fore part a bones (h), the two Palate, the two Malar (1), the two Lacry-shallow depression, in which the lachrymal gland is lodged, mal (j), the two inferior Turbinated, the Vomer (k), and the inferior Maxillary (7).

The frontal bone (Fig. 11, a, b) forms the forehead and the roof of the orbit. The front or frontal portion is the larger. Its anterior surface, which is represented in Fig. a, is convex and smooth: it is bounded below by two arched, thick, and rounded borders, separated by a rough notch in the middle ime. The borders (1, 1) are called the orbital arches or ridges, and they form the front and prominent part of the ortits. The notch (2) is named the nasal notch;

and at its inner and fore part a mark to which the pulley of
the trochlearis muscle of the eye is attached. The upper
surface is marked in correspondence with the irregularities
of the under part of the anterior lobe of the brain, which
rests upon it.

The posterior and upper margin of the frontal bone (b, 5,
5) is joined by the coronal suture to the two parietal bones;
and it is cut obliquely in such a manner that its edges rest
upon theirs above, and theirs overlap its below. The lower
part of this margin is covered by the ala of the sphenoid,

per jaw, and i

nd on a proces tremity of en ,4), and at th ess (5, 5); the

er with the rnal processi hrough whe e orbit to th

rounded elev rks the site ities, betwe

They ra municate e middle Ea urface of t ge (8,8) e rest of t

erent perse . On exter border al fossa which is

where they rise into the temporal fossa. The frontal is
usually in the adult only a single bone, composed (as all the
bones in the middle plane of the skeleton are) of two equal
and similar halves: these are developed separately, and
they sometimes remain undivided by a continuation of the
sagittal suture which passes from between the two parietal
straight down the middle of the frontal.

k

3

Fig. 12.

The construction of the Parietal bones, which form all the upper and middle part of the skull, is very simple. In Fig. 12 at a the exterior, and at b the interior, of the right parietal is represented. They are quadrilateral, and of nearly equal thickness throughout. The outer convex surface is everywhere smooth, except at its lower border (1), where it is overlapped by the Temporal bone in the squamous suture, and just above this part, where there is a slight arched ridge (2), for the attachment of a portion of the temporal muscle. The inner concave surface has impressions of the cerebral convolutions, and a deep branching groove, which, beginning at the fore and lower angle (3), thence ramifies diffusely. It lodges the middle meningeal artery of the dura mater. [BRAIN] Along the upper border is a broad shallow groove (4), which lodges part of the longitudinal sinus, and is continuous with that on the interior of the frontal bone. The borders of the parietal bones are all, except the lower, deeply and irregularly indented; and by the dovetailing of such irregular teeth, they form, with the frontal bone in front, the coronal suture, with the occipital behind, the lambdoidal, and, in the middle line at their own meeting, the sagittal.

The Temporal Bones (Fig. 13, as seen from without) are placed in the middle, lateral, and inferior parts of the skull. They present each three distinguishable parts, which in the foetus are separated namely, a Squamous portion (1), which forms the middle of the side of the skull; a Mastoid portion (2), which forms the thick protuberance that may be felt behind the ear; and a Petrous portion (not visible in Fig. 13, but in Fig. 10 marked c), which passes from the lower part of the squamous forwards and inwards in the Fig. 13.

base of the skull. The squamous bone or portion has a roundish form. Its upper edge covers in the lower border of the parietal. Its exterior surface is smooth, and gives

attachment to some of the temporal muscle. At the hinder part of its lower border is an oval aperture (3), leading to the meatus auditorius externus [EAR], a passage which goes forwards and inwards to the tympanum in the interior of the petrous portion. Immediately anterior to this, and under the fore-part of the bone, is the Glenoid cavity (4), a deep transversely oval hollow, with which the condyle of the lower jaw is articulated, and behind which is a narrow chink, the Fissura Glaseri, separating it from a strong ridge which runs along the upper surface of the petrous bone. In front of the glenoid cavity is a prominence, which forms its border, the Tuber articulare (5); and from its outer part there proceeds horizontally forwards, as if springing from the tuber and two other slightly elevated lines running backwards, a long narrow portion of bone, the Zygomatic process (6), the enlarged end of which joins a short process of the malar bone to form the zygoma, an arch beneath which the temporal muscle plays, and whose size and strength are generally in direct proportion to those of that muscle, and to the force with which the lower jaw is worked in gnashing with the teeth.

Behind the meatus auditorius is the mastoid portion. It is prolonged downwards in a strong conical projection, the mastoid process (7) giving insertion to muscles upon and just above it, and of which the interior is occupied by numerous cells communicating with the cavity of the tympanum. Behind and within the mastoid process is the digastric groove, to which the muscle of the same name is attached; and farther back another more shallow groove for the trachelo-mastoid muscle.

The cerebral surface of the squamous portion has a very obliquely cut and groved upper border, which articulates with the lower border of the parietal bone. On the same surface of the mastoid portion is a deep fossa, which lodges part of the lateral sinus. Both are marked by the impressions of the brain.

The Petrous process or portion of the temporal bone (Fig. 10, c), has received its name from the peculiar hardness of its tissue. It has the form of an irregular three-sided pyramid, directed from either side forwards and inwards, and fitting, at the base of the skull, into the angle left between the sphenoid and the occipital bones (e and d). Its base is affixed to the interior and lower part of the squamous bone; its summit fits in the apex of the angle just mentioned. On its posterior surface the most prominent object is the oval aperture of the meatus auditorius internus, the passage leading to the internal ear, and traversed by the auditory and the facial nerves. On the anterior surface there are a shallow groove leading to a small hole, through which the Vidian nerve and bloodvessels pass, a slight hollow on which the Gasserian ganglion of the fifth pair of nerves lies, and a prominence which indicates the position of the superior semicircular canal of the ear. On the inferior surface, which is placed outside the skull, there are seen, at the posterior and outer border, a deep fossa (the Jugular), in which the upper part of the internal jugular vein is lodged; before and on the inner side of this, and separated from it by a prominent ridge, a large oval aperture, through which the internal carotid artery passes into a tortuous canal, whose other extremity is at the very apex of the bone; between the jugular fossa and the mastoid process a hole, the Stylo-mastoid foramen, through which the facial nerve passes on its way to the face, after penetrating the bottom of the meatus auditorius internus; and just anterior to this, a long-pointed process, the Styloid (8), to which several muscles and ligaments are attached, and whose base is surrounded by an irregular sharp-edged elevation, the Vaginal process (9).

The anterior border of the petrous bone is articulated with the posterior part of the ala of the sphenoid, leaving an intermediate space, named foramen lacerum medium; the posterior border is similarly united with the side of the basilar process of the occipital bone, leaving another space, the foramen lacerum posterius, through which the internal jugular vein and the nerves of the eighth pair pass. Near the angle where the anterior border joins the squamous bone is an irregularly shaped aperture, to which the cartilaginous part of the Eustachian tube is affixed.

The small bones of the internal Ears, and all the other parts of the organ of Hearing, which lie within and near the petrous bone, are already described. [EAR.]

The Occipital Bone (Fig. 14 18 a view of the internal surface) forms the posterior and lower part of the middle of

Fig. 14.

1

the skull, a portion being at the outer wall and a portion at the base. Its lower and anterior part is narrow, and has a rough surface (1) in front, which is united with the body of the sphenoid bone. Viewing it at its internal surface, it presents, as one proceeds from this surface backwards and upwards, a smooth hollow surface, which gradually widens, and is limited behind by a large oval opening. The surface (2) is that of the Basilar Process, in which the medulla oblongata and pons Varolii [BRAIN] rest; the aperture (3) is the Foramen magnum, through which the medulla passes into the spinal canal, where it is continued into the spinal cord. By the sides of this foramen, near where the basilar process joins the back and expanded part of the bone, there are four foramina, two on either side, the anterior and posterior condyloid foramina, of which the anterior transmit the hypoglossal nerves, on which the motions of the tongue depend, and the latter give passage to veins communicating with the vertebral veins. Opposite the fore part of the foramen magnum the basilar process suddenly widens into the greater portion of the occipital bone, which forms the back of the head. In this part are four large hollows (4, 4, 5, 5), of which the two upper lodge the surfaces of the posterior lobes of the cerebrum, the two lower those of the lobes of the cerebellum. They are separated by two ridges, which bisect each other at nearly right angles. The upper part of that which runs vertically has attached to it a portion of the falx major, and to its lower part is affixed the falx cerebelli; that which runs transversely gives insertion to the back part of the tentorium cerebelli, whose anterior borders are fixed to the upper angles of the petrous bone. By these ridges are broad shallow grooves, which lodge parts of the sinuses of the brain. By the upper half of the vertical ridge is the extremity of the longitudinal sinus, the grooves for which, in the frontal and parietal bones, are already mentioned, and which, at the Internal Occipital spine, where the ridges bisect each other, meets the inferior longitudinal and other sinuses, to form what is named the Torcular Herophili, their common point of meeting. From this there proceed the two lateral sinuses, which run above the transverse ridge on either side, then cross over the posterior inferior angle of each of the parietal bones, then lie for a short distance on the inside of the mastoid portion of the temporal, from which they pass through the foramen lacerum posterius by a special aperture, marked by a deep notch in the border of the occipital bone, near the angle (6), which separates the basilar from the other portion.

The inferior and outer surface presents on the basilar process numerous irregularities, from which the back part of the pharynx is suspended, and into which certain muscles and ligaments of the front of the spine are inserted. The foramen magnum has here an even and grounded border; and by its sides two elevations, each with a smooth convex oval surface, whose larger axis is directed forwards, inwards, and downwards; these are the Condyles, by which the occipital bone articulates moveably with the first vertebra of the spine. Near these also are the outer orifices of the anterior and posterior condyloid foramina, and around them very rough surfaces for the insertion of ligaments and muscles. On the outer surface of the expanded posterior portion of the bone are three ridges, one of which passes from the border of the foramen magnum backwards and upwards in correspondence with the internal vertical ridge, and is crossed on its way by two transverse arched ridges. At the crossing of the upper of these two is a sharp prominence, the occipital spine or protuberance. The two trans

verse ridges and the spaces below them give attachment to muscles; the spine, to the ligamentum nucha. Above the upper ridge the surface is smooth.

The upper and lateral borders (7) of the Occipital bone are deeply toothed, and form the Lambdoidal Suture, with the parietal bones above and the mastoid below. In the course of this suture there occur, more often than in that of any other, insulated portions of bone, of various size and form, called Ossa Wormiana, surrounded by margins toothed as in the regular line of suture.

The Sphenoid Bone (Fig. 10, e) is placed in the middle of the base of the skull, and has a very complicate form. Fig. 15, a, gives a front, and b, a back and upper view of it. Its principal parts are described as a body (1, 1), two

Fig. 15.

a

Greater Alæ (2, 2), two Lesser Alæ (b, 3, 3), and, on each side, two Pterygoid Processes (a, 4, 4). The body is the central part, and has somewhat the form of a hollow cube. Chief part of its upper or cerebral surface is hollowed, forming what is called the Sella Turcica (b, 4), and lodging the pituitary gland. [BRAIN] It is bounded at its four corners by bluntly pointed prominences called Chinoid Pro cesses (see Fig. 10), to which prolongations of dura mater are attached. Between, and a little in front of the two an terior of these, is a level surface (b, 5) on which the commissure of the optic nerves rests, and which has behind a slight elevation, the Olivary process, and in front a pointed one, the Ethmoid spine (b, 6) which fits into the Ethmoid bone. The sides of the body slope obliquely downwards towards the great ale, and the cavernous sinus and internal carotid artery of each side rest against them. The posterior surface (b, 7) of the body is rough, and unites with the end of the basilar process of the occipital. The anterior presents the openings of large cells which occupy the whole interior. These are divided by a middle septum (a, 5), and are partly closed in by two small portions of bone called Sphenoidal Cornua; where not thus closed, they open into the posterior ethmoidal cells. The under surface of the body is chiefly flat, but has a ridge called the azygous process along the middle line, which fits to the Vomer.

The Greater Alæ (2) are affixed by the sides of the body,
and project from it outwards, upwards, and forwards. On
each there are three principal surfaces, turned towards the
brain, the temple, and the orbit, respectively. The inner
or cerebral (b, 8) is concave, supports part of the middle
lobe of the brain, and presents three particular orifices,
namely: the foramen rotundum, near its anterior and inner
margin, through which the superior maxillary nerve passes
from the Gasserian ganglion of the fifth pair; the foramen
ovale, much larger and near the posterior and inner border,
through which the inferior maxillary nerve goes from the
same ganglion; and the foramen spinosum, near the outer
and posterior angle, which transmits the middle menin-
geal artery. This outer angle (b, 9), which fits in between
the petrous and squamous parts of the temporal bone (see
Fig. 10), is named the spinous process. The outer or tem-
poral surface (a, 6) is slightly hollowed, and forms part of
the temporal fossa, rising up at the lower part of the side
of the skull as far as the anterior inferior angle of the parie-
tal bone. At its lower border it turns abruptly inwards at
a slight ridge, below which it is continued to the ptery-
goid processes, and forms part of the zygomatic fossa; its
posterior border articulates with the squamous, its anterior
with the frontal bone. The anterior or orbital surface (a, 7)

is flat and smooth, and forms part of the outer wall of the
orbit, where it articulates with the malar, frontal, and upper
jaw bones.

The Lesser Alæ (b, 3, 3) are long, narrow, sharp-pointed
processes projecting horizontally outwards from the front
and upper part of the body. Internally and behind they
bear the anterior clinoid processes, beneath which are the
Optic foramina for transmitting the ophthalmic arteries and
the optic nerves from the commissure to the orbit. The
upper surface of these ale is flat, and supports part of the
brain. The anterior border is articulated with the orbital
plates of the frontal bone on either side, and in the middle,
where the ethmoidal spine projects, with the ethmoid bone.
The posterior border lies in the Fissura Sylvii, between the
anterior and middle lobes of the brain. The under surface
is smooth: between it and the anterior edge of the great
ala is a gap, the foramen lacerum anterius, transmitting
nerves and a vein to the orbit.

The Pterygoid processes (a, 4, 4) are directed downwards
from the under and outer part of the body. On each side
there are two lamellæ, an external and an internal; they
are long and narrow quadrilateral plates nearly meeting in
front, where they articulate with the palate bone, and di-
verging behind so as to leave a space, in which the internal
pterygoid and circumflexus palati muscles are attached.
The internal and longer of the lamelle has at its lowest
extremity a hook, the Hamular process, round which, as on
a pulley, the tendon of the last-mentioned muscle plays.
At the upper part, where the pterygoid processes join the
body, is a canal, the Vidian, running from before backwards
and transmitting the Vidian nerve.

The Ethmoid Bone (Fig. 10, f) is situated in the front
and middle part of the base of the skull, between the orbits.
Fig. 16 gives a profile view of it from the left side.. It pre-
sents six different aspects, and for the most part is of a very
light spongy texture. Its upper surface, which is presented
to the brain, has in front and in its middle line a strong
triangular process, the Crista Galli (1), to which the front
of the falx cerebri is attached. The apex of this process is
directed straight upwards; the base is continuous below
Fig. 16.

2

1

spectively the Superior and the Middle Meatus of the nos?. The ethmoidal cells communicate in front with the frontal, and behind with the sphenoidal cells or sinuses.

The six bones just described enclose the Brain, forming a cavity whose size, compared with that of the crania of brutes, is one of the most distinguishing marks of the human species. To the protection of the important organs within it, as to their chief office, everything in the structure and arrangement of the bones of the cranium is adapted. Those parts of them which lie exposed to direct external injury are formed of three layers, namely, an outer and inner table, and an intermediate diploe.* The outer table is formed of bone of ordinary compactness, such as is not liable to be cracked by moderate shocks; the inner, of much harder and more brittle bone (whence its name of Tabula vitrea), which may be more easily cracked, but less easily cut or pierced. The diploe is of a soft spongy tissue, calculated to lessen the vibrations that are produced by blows on the outer table, before they reach the inner and more brittle one. The arrangement is thus similar to that by which one might safely enclose a substance liable to injury either from being shaken or cut, within an inner case of hard porcelain, a middle one of soft leather, and an outer one of tough wood.

The formation of the sutures seems to have the same end. The outer tables of the exposed bones have their edges finely dovetailed, and are thus so immoveably held together that none but a violently expansive force exercised at once on the whole interior of the cavity can separate them. The inner tables are simply apposed with a very thin intermediate layer of cartilage; an arrangement which, as Sir Charles Bell (who has written most ingeniously on this subject in his 'Animal Mechanics'), says, is often imitated in works of art, in which tough materials, such as wood, are joined by mutually fitting dentations; and brittle ones, such as glass or marble, by smooth edges and a layer of cement. A similar mode of opposition is seen between all the bones of the skull that are not exposed to direct violence.

The top of the skull presents transversely an arch formed by the two parietal bones (see Fig. 8), whose most prominent parts, like those of the frontal, occipital, and others, are stronger and thicker than any others; a circumstance adapted for greater resistance to force, whether applied directly against those parts, or to the summit of the arch from whence it would fall chiefly on them. The strength of this arch is further secured by the lower parts of the parietal bones being held in by the overlapping upper borders of the temporal and sphenoidal bones, other parts of which, passing across the base of the skull, hold the parietal bones, which by pressure from above might be made to start outwards or with the perpendicular or nasal plate (2), which divides the pushed inwards, as beams hold the walls of a house from Ethmoid bone into two equal lateral halves, and which, being driven either in or out by the weight of the roof. with the Vomer, which it joins below, forms the greater Taking the whole upper part of the skull as a dome, the part of the septum of the nose. The Crista Galli, sloping same strength of resistance to superincumbent pressure is downwards and backwards, is gradually lost behind, where obtained at every part by nearly similar means, especially at the Ethmoid bone receives the spine of the sphenoid. On at the coronal suture, where, as has been already said, the either side of it is a narrow quadrangular plate (the Cribri-parietal bones overlap the frontal at the supports of its arch, form plate), on which the bulb of one of the olfactory nerves and are themselves overlapped by it at the summit of their rests. Each is perforated by a number of holes through own. In this regard also may be noticed the strength and which the branches of the olfactory and another smaller thickness of the angular processes, and of the orbitar arches nerve pass to the interior of the nose. In front, and along extended between them (see Fig. 11), which serve as suppart of the border or each plate, are the orifices of numerous ports for the front of the dome; and the thickening of the cells, which, in the entire skull, are closed in by the frontal bones along the course of the longitudinal and lateral sinuses, bone and its orbitar plates, and communicate with the resembling groins in masonry. frontal sinuses.

The surface of the upper part of each side of the ethmoid bone is formed by a thin smooth quadrilateral plate, the orbitar plate (3), which forms great part of the inner wall of the orbit, and unites above with the corresponding plate of the frontal (leaving two small apertures, the anterior and posterior internal orbitar foramina, for the passage of small nerves and vessels), in front with the lacrymal, below with the orbitar portions of the upper jaw and palate bones, and behind with the sphenoid. Between the orbitar and nasal plates, each half of the bone is formed of cells and folds of very thin lamellæ, which form part of the chambers of the nose, and have the olfactory membrane and nerves spread out upon them. [SMELL.] The principal parts are the middle turbinated or spongy bone (4), a roll of thin bone, which forms the lower border of the cells; and a smaller but similar roll higher up, and confined to the back part, called the superior turbinated or spongy bone (5). Under each roll at its posterior part is a passage to the cells, called reP. C., No. 1369.

The relations of the skull to the erect posture, the adaptations of the ethmoid and sphenoid bones to the sense of smell, and the arrangements of the base of the skull in reference to the ear, the several nerves, &c., are considered elsewhere. [BRAIN; EAR; MAN; SMELL, &c.]

The second chief division of the Skull includes the bones of the Face, the principal of which are represented in Figs. 8 and 17.

The Nasal Bones (Figs. 8, 9, 17, g) form the upper part of the bridge of the nose. They are narrow and quadrilateral; thick above, where they fit into the nasal notch of the frontal bone; broad and thin below. The outer border of each articulates with that of the ascending process of the upper jaw-bone; the inner is in contact with that of the other; the lower are in contact with the cartilages that form the rest of the groundwork of the nose. The anterior sur

This arrangement does not exist in either the child or the old person. In the former all the bones are tough and elastic; in the latter the diploe is filled up by hard bone, and the whole cranium is therefore more liable to fracture. VOL. XXII.-M

f