140 



THE NOSE. 



and the remainder is divisible into two parts, viz., the upper or olfactory region in 

 which the epithelium is non-ciliated and columnar, and the lower or respiratory 

 region in which, as also in the sinuses, it is ciliated and columnar. The membrane 

 in the respiratory part covers the middle and inferior turbinals and all the lower 

 portions of the fossae, and is studded with racemose glands, which open by orifices 

 apparent on the surface. They are most numerous about the middle and hinder 

 parts of the nasal fossae, and are largest at the back of the septum near the floor of 

 the nasal cavity. Glands which are much smaller and less numerous are stated to 

 open into the several cavities which communicate with the nasal fossae, but many 

 observers have failed to find them. Besides the glands the mucous membrane of 

 the fossae contains a variable amount of lymphoid tissue, occasionally accumulated 

 into " nodules." In some parts large venous plexuses are found, encircled, as well 

 as the alveoli of the glands amongst which they lie, by bundles of plain muscular 

 fibres (Klein), thus forming a sort of cavernous tissue. 



Olfactory mucous membrane. The olfactory region, or that in which the 

 olfactory nerve is distributed, includes in man only the uppermost part of the fossae 



Fig. 158. SECTION OP THE OLFACTORY MUCOUS MEMBRANE. (Cadiat.; 

 a, epithelium ; 6, glands of Bowman ; c, nerve-bundles. 



(superior turbinal and corresponding part of the septum). It is extremely vascular, 

 a close plexus of large capillary vessels being found under the lining membrane 

 throughout its whole extent. Its mucous membrane is covered by a very thick 

 non-ciliated epithelium, and it is more delicate in consistence than that of the 

 ciliated region, being indeed soft and pulpy. It has a distinct yellow colour in 

 man (locus luteus) ; brown in some animals ; the colour may extend however 

 beyond the true olfactory part of the mucous membrane. The glands of this 

 region (glands of Bowmati) are numerous, and are of a more simple structure 

 than those in the lower part of the fossae. They open by fine ducts lined with 

 flattened cells which extend to the surface between the olfactory epithelium cells 

 (fig. 158). In the mucous membrane itself, the gland-tube is somewhat convoluted 

 and enlarged, and it may have one or two branches. It is limited throughout by a 

 basement membrane, and lined and almost filled with columnar or polyhedral 

 secreting cells. These are of the "serous" type in man, but in some mammals 

 there are " mucous " cells intermingled with the serous (Paulsen). The gland-cells 

 contain yellowish brown pigment. In man the gland-ducts frequently open into a 

 small sub-epithelial receptacle lined with flattened epithelium, from which a fine 

 tube passes to the surface between the epithelium cells. Occasionally the opening 



