710 THE EESPIEATOEY TEACT. 



tory and an olfactory portion. At its beginning the wall of the 

 nasal cavity has the same structure as the skin. It is freely sup- 

 plied with hairs and sebaceous glands, and covered by a stratified 

 epithelium. Behind the pyriform aperture the stratified epithe- 

 lium is changed into columnar, ciliated epithelium, whose cilia are 

 directed toward the choanae. The connective tissue producing 

 the mucous layer is abundantly supplied with acinous glands, 

 which produce a serous secretion. Toward the upper narrowed 

 olfactory portion of the nasal cavity the ciliated epithelia disap- 

 pear and are replaced by simple columnar epithelia. 



In the lateral cavities, which are in connection with the nasal 

 cavity, the thin mucosa is covered with ciliated epithelia, but the 

 acinous glands are very scanty. According to E. Zuckerkandl, 

 in the upper wall of the maxillary sinus there is a tongue-shaped 

 portion of the mucosa, richly supplied with glands; this portion 

 is characterized to the naked eye by a pale yellow color. The 

 mucosa of the nasal cavities has an abundant vascular supply, the 

 veins being wide and united into a plexus. On the convex surface 

 of the concha, more particularly at its posterior extremity, the 

 veins produce a cavernous tissue (Henle). In the lateral cavities 

 the blood-vessels are far less numerous. 



The olfactory portion of the nasal cavity is, according to M. 

 Schultze, limited to its roof to the upper turbinated bone, except 

 the lower border, and to the upper portion of the septum narium. 

 This portion is characterized by a yellowish color, the mucosa 

 being broader than in the respiratory portion, and freely sup- 

 plied with nerves and tubular glands, and, as a rule, also with 

 clusters of brownish pigment. 



The epithelial lining attains, in this situation, a considerable 

 size, and, as M. Schultze discovered, is composed of columnar 

 epithelia, between which are lodged the olfactory epithelia. The 

 latter consist, according to him, of a fusiform, nucleated body, 

 occupying the lower portion of the epithelial row, with polar 

 prolongations of varying lengths. The peripheral offshoot ex- 

 hibits varicose enlargements, and in many animals holds on its 

 surface delicate cilia, which have no analogue in man. The 

 central offshoot has the features of non-medullated nerve-fibers, 

 and very probably is in direct union with the terminal branches 

 of the (non-medullated) olfactory nerve. The feet of the col- 

 umnar epithelia proper exhibit pencil-like ramifications, serving 

 for their attachment to the subjacent connective tissue, and are 

 often supplied with brown coloring matter. According to S. 



