382 



NORMAL HISTOLOGY. 



Supporting cell 



Nerve-fibre 



FIG. 427. Section of olfactory mu- 

 cous membrane, silver preparation ; 

 two olfactory cells are seen, one 

 sending nerve-fibre towards the 

 brain. X 335. (Brunn.) 



FIG. 428. Isolated ele- 

 ments of epithelium of olfac- 

 tory mucous membrane; a, 

 pltactory cells; b, support- 

 ing cells. X 600. (Brunn.) 



slightly beyond the general level of the epithelium and bears from 6-8 minute 

 stiff cilia, the olfactory hairs. Being dependent upon the position of the 

 nuclei, the length of the peripheral processes varies, since the nuclei occupy 

 different levels within the epithelium in order to accommodate their great 



number. The central processes of the olfactory 

 cells, much more delicate than the peripheral, 

 are directly continued, as the axis-cylinders, 

 into the subjacent nonmedullated iv^rve-nbres 

 within the tunica propria, 

 from which they pass 

 through the cribriform 

 plate of the ethnoid to 

 enter the brain and end in 

 the arborizations within 

 the olfactory glomeruli of 

 the bulbus olfactorius. 



The tunica propria 

 I is differentiated into a su- 



perficial and a deep layer 

 by the lymphoid charac- 

 ter of the stratum directly 

 beneath the epithelium. 

 The superficial layer, from 

 15-20 fj. thick, consists of 

 closely packed irregularly round cells, resembling lymphocytes, and meagre 

 bundles of delicate connective tissue. The deep layer, on the other hand, 

 contains robust bundles of fibre-elastic tissue and relatively few cells. 

 A distinct membrana propria is wanting within the olfactory region. 



The olfactory glands, or glands of Bowman, are characteristic of the 

 olfactory region and elaborate a thin and watery secretion. They open 

 onto the free surface by very narrow ducts that lead into saccular fusiform 

 dilatations, the ampulla, into which the tubular alveoli pass. The ducts 

 possess an independent lining of flattened cells, that extend as far as the 

 surface and lie between the surrounding epithelial elements. The dilatations 

 are clothed with flattened or low cuboidal cells, which are replaced by those 

 of irregular columnar or pyramidal form, often pigmented, within the tubular 

 alveoli. From the character of their secretion, the glands of Bowman are 

 probably to be reckoned as serous and not mucous. 



The Respiratory Region. The mucous membrane lining the res- 

 piratory region differs greatly in thickness in various parts of the nasal 

 fossa. In situations where the contained cavernous tissue is well repre- 

 sented, as over the inferior turbinate, it may reach a thickness of several 

 millimeters, while when such tissue is wanting, as on the lateral wall, it is 

 reduced to less than a millimeter. 



The epithelium is stratified ciliated columnar in type, from 50-70 ft 

 thick, and includes the tall ciliated surface cells, between whose inner ends 

 lie the irregularly columnar basal cells. Numerous elements exhibit various 

 stages of conversion into mucus-containing goblet-cells. The current produced 

 by the cilia is towards the posterior nares. Intraepithelial migratory lympho- 

 cytes are also common. Beneath the epithelium stretches the membrana 

 propria, that varies greatly in thickness; although in certain localities 

 feebly developed, it is usually well marked and measures from 2-10 it in 

 thickness. Under pathological conditions its thickness may increase four- 



