from the spheno-palatine ganglion, and the orbital branch of the superior maxillary nerve.

How is the inferior internal angle formed?

By a suture, the union of the lacrimal and os planum of the ethmoid with the superior maxillary and palate bones.

What foramen does the orbital margin present?

The supra-orbitals at the junction of the inner and middle thirds, transmitting the supra-orbital artery, veins, and nerve.

What foramen opens at the apex of the orbit?

The optics, between the two roots of the lesser wing of the sphenoid, transmitting the optic nerve and the ophthalmic artery.

Mention the nine openings communicating with the orbit. The optic 1, sphenoidal fissure" (foramen lacerum anterius), spheno-maxillary fissure 26, infra-orbital canal, anterior and posterior ethmoidal foramina, malar foramina 1, supra-orbital foramen, and lacrimal canal 20 (occasionally, in addition, one or more external orbital foramina in the wing of the sphenoid).

17

Describe them.

The Nasal Fossæ.

19

They are two irregular cavities, extending from the base of the cranium above to the roof of the mouth below, separated in the median line by a thin osseo-cartilaginous septum, open

Roof

Outer Wall

Nasal Proc. of SupMar
Lachrymal
Ethnoid

Unciform roa of Eth.
Inferior Turbinated
-Palate

Superior Meatus

-Middle Meatus
Inferior Meatie

FIG. 34.-Roof, floor, and outer wall of the left nasal fossa (Gray).

ing upon their facial aspect by two large apertures, the anterior nares, and into the pharynx by the posterior nares. Each fossa communicates with four sinuses and four cavities (Fig. 34).

Of what parts is the nasal septum composed?

In front the crest of the nasal bones and the frontal nasal spine; its middle portion, the vertical plate of the ethmoid; behind, the rostrum of the sphenoid, the vomer, and the sphenoidal crest; below, the crests of the superior maxillary and palate bones.

What points does the roof of each fossa present?

In front the slit for the nasal nerve; numerous foramina for the olfactory filaments; the spheno-ethmoidal recess, and most posteriorly the opening of the sphenoidal sinus.

The floor?

In front the anterior nasal spine; behind this the opening of the anterior palatine canal and the palate processes of the superior maxillary and palate bones; internally, the nasal and the incisor crest; posteriorly, the posterior nasal spine.

Describe the chief points in the outer wall of each fossa.

This presents three irregular longitudinal passages, formed by three projecting bony plates, called the superior, middle, and inferior meatuses.

Describe each meatus.

The superior occupies the posterior third of the wall, lies between the superior and middle turbinated bones (processes of the ethmoid), and has opening into it two foramina, the spheno-palatine posteriorly and the posterior ethmoidal cells in the front part of the upper wall.

The middle occupies the posterior two-thirds of this wall, lies between the middle and the inferior turbinated bones, and has opening into it in front the infundibulum; in its center, the antrum of Highmore.

The inferior lies between the inferior turbinated bone and the nasal floor, extends along the whole length of the outer wall, and has opening into it, in front, the lower orifice of the canal for the nasal duct (and the anterior palatine canal in the macerated bone, not in the natural state).

Describe the position and boundaries of the temporal fossa.

Situated at the lateral region of the skull, each fossa is

marked out upon the skull-cap by the temporal ridge, which extends in a curved line first upward and backward from the external angular process of the frontal bone, then downward behind to form the posterior root of the zygomatic process. Its anterior boundaries are the frontal, malar, and greater wing of the sphenoid; above and behind, the temporal ridge; below, the pterygoid or infra-temporal ridge on the greater wing of the sphenoid; externally, the zygomatic arch; it opens below into the zygomatic fossa, is filled by the temporal muscle, and is traversed by grooves for branches of the deep temporal artery.

Describe the zygomatic fossa, its boundaries and communicating fissures.

It is bounded anteriorly by the tuberosity of the superior maxilla and the ridge descending from its malar process; superiorly, by the infra-temporal ridge of the greater sphenoidal wing and under part of the squamous plate of the temporal; behind, by the posterior border of the pterygoid process; below, by the alveolar border of the superior maxilla; internally, by the external pterygoid plate; and externally, by the ramus of the lower jaw and the zygoma. The spheno-maxillary and the pterygo-maxillary fissures open into its upper part.

What does it lodge?

The internal and the external pterygoid and part of the temporal muscle, the internal maxillary artery, and the inferior maxillary nerve, and their branches.

Describe the spheno-maxillary fissure.

It runs horizontally, opens into the outer back part of the orbit, lying between the lower orbital border of the greater wing of the sphenoid and the outer border of the orbital plate of the superior maxilla and a small part of the palate bone; externally is a small part of the malar, while internally it joins the pterygo-maxillary fissure at a right angle; it transmits the infra-orbital vessels, the superior maxillary nerve, with its orbital branch, ascending branches from Meckel's ganglion, and serves to connect the orbit with the spheno-maxillary, temporal, and zygomatic fossæ.

What are the boundaries of the pterygo-maxillary fissure, and what passes through it?

It is bounded in front by the maxillary tuberosity; behind, by the pterygoid plate of the sphenoid; descends at right angles from the inner extremity of the spheno-maxillary fissure, transmits branches of the internal maxillary artery, and connects the zygomatic and the spheno-maxillary fossæ.

Describe the spheno-maxillary fossa.

Situated at the junction of the spheno-maxillary and the pterygo-maxillary fissures, it is bounded above by the under surface of the body of the sphenoid; in front by the superior maxillary bone; behind, by the pterygoid process and the lower part of the anterior surface of the great wing of the sphenoid; internally, by the vertical plate of the palate with its orbital and sphenoidal processes. In this fossa terminate the sphenoidal, spheno-maxillary, and pterygo-maxillary fissures. Four fossa communicate with it, the orbital, nasal, zygomatic, and the middle cranial fossæ.

How many foramina open into it?

Five (sometimes seven or eight); three in the back wall, viz. above, the foramen rotundum; more internal and inferior, the Vidian; and lowest and most internal, the pterygo-palatine; on the inner wall is seen the spheno-palatine foramen; below, the upper orifice of the posterior palatine canal, and sometimes two or three accessory posterior palatine canals. This fossa is thus connected with three fissures, four cavities, and five fora

mina.

BONES OF THE TRUNK, AXIAL SKELETON. The Vertebral Column.

How are the vertebræ divided?

Into five regions, viz. cervical (7); thoracic (12); lumbar (5); sacral (5); and coccygeal (4); 33 in all.

What are the sacral and coccygeal vertebræ called to distinguish them from the remaining bones?

False or fixed vertebræ, the others being called true or movable vertebræ.