The lower ;van or floor of the nasal cavity is nearly horizontal ; it is concave transversely, a little raised at each end, and narrower before than behind. It is formed by the upper sur faces of the palatine plates of the superior max illary and palate bones, and its inner burder is a little prolong,ed both behind and before upon their nasal spines. Near its anterior border it is perforated by die superior orifice of the anterior palatine c.anal.
The outer wall is the most complicated. (Fig. 399.) If a vertical line be drawn down wards from the base of the nasal spine of the frontal bone (a), it will have in front of it the plain part of this wall, a slighty concave tri angular surface, formed by the ascending pro cess of the superior maxillary bone (b), and presenting nothing but soine shallow grooves for bloodvessels and nerves. And, if a similar line be drawn downwards from the front of the body of the sphenoid bone (c), it will have behind it another plane surface formed by the internal pterygoid plate (d). Between these vertical lines there is a large quadrilateral sur face divided into three parts by the three tur billeted bones, whose edges project in nearly parallel and horizontal lines, at about equal distances one above the other. At the upper part of this surface and anteriorly is a thin quadrilateral plate (e) belonging to the cellular portion of the ethmoid bone, made very rough by grooves and apertures which lodge branches of the olfactory nerve. The anterior part of this plate forms the inner wall of the anterior ethmoidal cells ; the posterior part (f) is a little curved outwards,. and leaves a space between its surface and the body of the sphe noid bone into which the sphenoidal sinus opens. The lower border of this plate is con tinuous anteriorly with the inner surface of the middle turbinated bone, and posteriorly has a free margin which is slightly curled outwards. From the form of this margin the plate is called the superior turbinated bone, (cornet sup rieur ; oberste Afuschel;) and the space which' it here covers and which is a kind of horizon tal channel between its outer surface and the wall of the adjacent ethmoidal cells, is the superior tnentus of the nose. Into this meatus the posterior ethmoidal cells open, usually by two or more orifices concealed by the turbinated bone; behind and a little below it is the spheno-palatine foramen (h), at which the nasal branches from the spheno-palatine ganglion and the spheno-palatine vessels enter the nose; and yet further backward, and nearly opposite the end of the superior turbinated bone, is the opening into the sphenoidal sinuses.
Below this upper plate, and continuous with it anteriorly, is the inner surface of the middle turbinated bone (g), another portion of the eth moid bone, (cornet moyen; mittlere A4 uschcl.) It is larg,er than thd superior, more convex on its inner surface, and presents a free marglil through the whole extent of its lower border which is thick, and abruptly curled outward; and sometimes has cavities within it (sinus? of Santorini), communicating with the eth moidal cells. The inner surface of the bone
deeply grooved and perforated hy bloodvi sql1 and branches of the olfactory and naso-pala tine nerves. Of dic grooves, those which lodi the olfactory nerves run from above downwards, and those in which the naso-palatine nerves lie are directed forwards ; at its lower margin also is a particular groove in which a large blood vessel runs. The outer surface is concave and smoother than the inner, and forms the inner boundary of the middle meatus of the nose. On the outer wall of this meatus, which is a much larger channel than the superior one, ex tending through nearly the whole length of the outer wall of the nasal fossw, there are pre sented from before backwards, after removing the turbinated bone,-1. a part of the ascend ing process of the upper jaw-bone; 2. part of the inner surface of the lachrymal bone ; 3. the walls of some of the anterior ethmoidal cells; 4. the infundibulum, a long, narrow, and slightly curved passage, leading obliquely upwards and forwards into the anterior ethmoidal cells, and through them into the frontal sinuses; 5. the entrance into the antrum, a large aperture of uncertain size and form ; and, lastly, a flat surface of the vertical plate of the palate bone.
Below the middle meatus is the inferior turbinated bone, the largest of the three, and usually described as a sepamte bone, because it is not so soon united to the adjacent bones. It is very uncertain in form and size; its depth especially varies; so that its lower border some times nearly touches the floor of the nasal ca vity, and sometimes is half an inch above it ; sometimes, also, it is so much curled outwards that it nearly forms a canal between its outer border and the outer wall. On the whole, however, this turbinated bone presents the sume general characters as the others. Its upper margin is fixed to a prominent ridge along nearly the whole length of the outer wall of the nasal fossm ; its lower margin is free, and its outer surface forms the inner boundary of the inferior meatus of the nose, of vvhich the outer boundary is formed by the ascending plates of the superior maxillary (k) and palate bones. At the anterior part of this meatus is the inferior orifice of the nasal canal, a passage flattened at its sides, larger at its extremities than in the middle, and passing, with a slight anterior cun-e, upwards, forwards, and a little outwards to the inner angle of the orbit. It lodges the nasal duct. At the level of this meatus also, behind the edge of the internal pterygoid plate, and about midway between the floor of the nose and the end of the inferior turbinated bone, is the opening of the Eusta chian tube; but nothing of this is seen in the skeleton.