THE NASAL CAVITIES. 



523 



Fig. 309. 



of the inferior or anterior compartment of these osteo-cartilajsfinous columns. It 

 also penetrates, by the semicircular openinj^ of this meatus, into the sinus, to give 

 it its mucous liuinjr, and is likewise prolonged into the canal of Jacobson. 

 Behind, it is continuous with the lining membrane of the pharyngeal cavity. 



Its deep face is separated by the periosteum or perichondrium, from the bony 

 or cartilaginous walls on which it is spread ; and it is united to the two precited 

 layers, tliis miion being closest where it is thinnest, although it can always be 

 easily distinguished from them throughout the whole extent of the nasal fossa. 

 The free, or superficial face, presents numerous glandular orifices, and is constantly 

 covered by an abundance of mucus, that prevents the desiccatiou to which this 

 surface is exposed by the incessant movement of air over it. 



Structure. — The organization of the pituitary membrane resembles that of 

 other mucous membranes, but it also presents some differences according as 

 it is examined near the nostrils or deeper in the cavities. It is also usual 

 to divide it into two portions — the olfactory mucous 

 membra HP, which covers the upper part of the ethmoidal 

 turbinated bone and cells ; and the Schneiderian mpm- 

 brcine, lining the inferior two-thirds of the nasal cavities. 



The car turn {tunica pro2)ria) of the Srhneiderian mem- 

 brane {reyio respirotoria) is thick, soft, spongy, and rose- 

 coloured, and contains a large nmnber of vessels and 

 glands. The latter are mucus or racemose glands, uud 

 are extremely abundant in the layer covering the septum 

 of the nose, as well as at the inner face of the carti- 

 laginous appendages of the turbinated bones ; though 

 they are rare or altogether absent on the external face 

 of the latter. The epithelium is ciliated and stratified, 

 the deeper cells being spherical, those on the surface 

 cylindrical. 



The olfactory mucous membrane (regio olfactoria) 

 differs from the preceding by its greater thinness, its 

 delicateness, its slightly yellow tint, and the character 

 of its epithelium. The corium (tunica proj/ria) contains 

 straight or slightly convoluted tubular glands — the glands 

 of Bowman. The epitlielium is columnar and stratified, 

 and readily alters ; in animals it is destitute of cilia. 

 The deeper cells contain some yellowish pigment granules. 

 Schultze describes as olfactory cells, certain fusiform 

 elements which he considers are concerned in olfaction, 

 prolongations — a deep one, which is connected with the fibres of the olfactory 

 nerve ; and a superficial, that enters between the epithelial cells, and tends to 

 approach the free surface of the membrane. 



(The " olfactory cells " are thin, rod-like bodies (Fig. 309, h), presenting 

 varicose enlargements which are connected with processes of deeper-seated nerve- 

 cells. The epithelial cylinders proper (f/, e) are related at their bases with the 

 septa of connective tissue belonging to the sub-epithelial glandular layer, and are 

 probably in communication with the olfactory cell. Schultze describes another 

 set of epithelial cells {a) as terminating externally by truncated flat surfaces, and 

 to all appearance not covered by any membrane, apart from the contents of the 

 cell, which are yellow, granular protoplasm, smrounding an oval nucleus lying 



CELLS OF THE OLFACTORY 



MUCOUS MKMBRANE. 



a, h, c, .After Schultze; 

 d, e, /, after Lock hart 

 Clarke. 



These cells have two 



