The free surface of that portion of the mu cous membrane which lines the proper cavities of the nose is smooth. It presents the orifices of many simple follicles or crypts. They are most numerous about the lower and anterior parts of the walls of the fossm, are of various sizes, and in many places lie in groups or rows. The follicles themselves are hemispherical, or, deep and more or less elongated. At the lower and anterior part of the septum, there is often a single long duct runninc, horizontally and leading to a collection of grand-cells which all appear to open into it ; and, generally, some others of the larger orifices are connected w ' composite glands.
The epithelium of the nose is, in part, of laminated, in part of the ciliary, kind. lien says that if an imaginary plane section of nose be made from the anterior free border the nasal bones to the anterior nasal spine the superior maxillary. bones, all the inucous membrane below and m front of this plane is covered by laminated epithelium, and all alm‘e and behind it by ciliary epithelium. The !anal covers not only all the walls of the nasal fossIt but is continued from them to the surftce the mucous membrane lining all the supple mental cavities, the nasal duct and lacrymal sae, and the upper part of the pharynx.
The course (as it is called) of the mucous membrane next merits consideration. Ascend ing from the floor of the nasal fossa up the outer side of the inferior meatus, it becomes gradually thicker and more spongy. From this meatus it is continued anteriorly into the nasal duct, around whose lower orifice it forms an annular fold or reduplication. The orifice in the bones is elliptical and rather obliquely placed, its anterior edge being somewliat lower than the posterior. The fold of mucous mem brane around it is especially deep on the inner side and posteriorly, and not only contracts the size of the orifice, but acts as a valve to guard it, and, when pressed upwards and for wards, to close it. Hence, though some per sons can inflate their lachrymal sacs, in most men, when the nostrils are closed,"and air is pressed forcibly into the nose from behind, none ever escapes from its cavities.
As the lining membrane descends again upon the outer surface of the inferior turbinated bone, it becomes thicker, more spongy, and more vas cular. At the lower edge of the bone it forms a deep fold, which, in its congested state, touches the floor of the cavity. The fold is peculiarly thick at the two ends of the bone, and in disease in scrofulous children it sometimes forms a loose and very vascular spongy mass, which has heen mistaken, it is said, for a poly pus. Immediately behind the deep posterior fold the Inembrane becomes again thin and ad heres closely to the pterygoid plate of the sphenoid bone, behind- which, and on a level with the extremity of the inferior turbinated bonC, it is continued into the orifice of the Eustachian tube.
As it passes front the inferior turbinated bone to the outer wall of the middle meatus, the Schneiderian membrane becomes again thinner and more compact. About the middle of this meatus it enters the deep channel of the infun dibultim, whose form it searcely alters, and along which it passes to the anterior ethmoidal cells, and through them to the frontal sinuses., Above the commencement of the infundibulum it enters into the antrum by a narrow orifice directed obliquely from before backwards. Of the great opening into the antrum when the superior maxillary bone is separated, a large portion is covered by the palatine and turbi nated bones ; and of what remains, all but a narrow circular orifice at the upper and anterior part is closed by a thick annular fold of the mucous membrane; and even permanent closure is DO rare consequence of the swelling to which the membrane is subject. Cloquet* says that this fold contains in man a gland vvith numer ous orifices analogous to one of large size which surrounds the orifice of the antruni in many animals. I have not been able to find such a structure, and even E. II. Wehert has not been more successful.
The membrane covering the middle turbi nated bone and the anterior portion of the cel lular part of the ethmoid is thick anti spongy, but less so than that on the inferior turbinated bone. In the superior meatus it is thin ; and it becomes still thinner as it passes into the one or more orifices of the posterior ethmoidal cells, on the borders of which it is tightly ap plied, and whose size, as it forms no loce pro jecting fold, it diminishes but little. It closes, at this part, the spheno-palatine foramen;and in the vault of the nasal fossae all the foramina of the cribriform plate, through which nerves and vessels are admitted to the outer surface of the mucous membrane, and the inner suiface of the periosteum. At the lower borders of the superior and middle turbinated bones it forms thick folds, which make the meatus appear far smaller than they do in the dry bones. These folds are not so deep as that on the inferior tur binated bone ; but, as they probably receive many filaments of the olfactory nerve, both they, and perhaps the inferior fold also, may be regarded as means for the multiplication of the sensitive surface, and as analogous, in some measure, to the folds of mucous membrane by which alone in Fish and the Proteus anguinus the same object is attained In all the rest of its extent over the septum, the nasal bones, and the lateral cartilages, the Schneiderian membrane has a uniform surface and is of about middle thickness : its layers are intimately united, and it adheres with mode rate firmness to the bone and cartilage.