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NORMAL HISTOLOGY. 



an outer cylindrical division, containing an oval nucleus, situated 

 always near the inner end of the more expanded part of the cell, and 

 yellowish pigment, together with numerous granules arranged 

 more or less markedly in longitudinal rows. The outer ends of the 

 supporting cells are modified into a cuticular zone, the membrana 

 limitans olfactoria, sometimes exhibiting vertical markings. 



The nuclei of the sustentacular cells form a regular band, the 

 zone of oval nuclei, which lies next the free surface, and strongly con- 

 trasts with the adjoining broad zone of round nuclei of the olfac- 

 tory cells. The inner portions of the sustentacular elements are 

 very narrow, irregular in outline, and terminate generally in cleft or 

 branched processes in close relation with the underlying basal cells. 



The olfactory cells lie among the supporting elements as incon- 

 spicuous, elongated, and attenuated bodies, whose variously-placed 

 spherical nuclei, covered by a thin stratum of protoplasm, consti- 

 tute the widest parts of the cells ; in consequence these elements 

 appear like spherules from the outer and inner poles of which thin 

 rod-like processes extend towards the free surface and the base- 

 ment-membrane. The nuclei of the olfactory cells lie at all levels, 

 forming the broad zone of round nuclei. 



The deepest part of the epithelial stratum is made up of a closely- 

 set zone of small nucleated cells, resting upon the tunica propria 

 on the one hand, and sending irregularly-branched processes among 

 the overlying elements on the other. These basilar cells consti- 

 tute a protoplasmic net-work, whose extensions and continuities are 

 at present inadequately determined. 



The tunica propria of the olfactory region consists of a moder- 

 ately loose felt-work of bundles of fibrous connective tissue, inter- 

 mingled with numerous delicate elastic fibres. The outermost zone 

 of the tunica propria is condensed to form a very slightly developed 

 basement-membrane, upon which rests the epithelium. Em- 

 bedded within the mucosa branched tubular glands, or Bowman's 

 glands, exist in great abundance ; these structures possess a duct of 

 sufficient length to extend through the epithelial layer, the remaining 

 portions of the tube constituting the body and fundus of the gland. 

 The epithelial cells lining the secreting part of the tube contain 

 brownish pigment, which aids in producing the characteristic color 

 of the olfactory mucous membrane. Although formerly regarded as 

 serous in type, it is probable that Bowman's glands must be included 

 within the mucous group. These glands, which in places consti- 

 tute an almost continuous layer of secreting tissue, are. much more 

 generously distributed than those within the respiratory region. 



The blood-vessels supplying the nasal mucous membrane are 

 especially distinguished by the size and profusion of the veins. 



