EAR 



479 



a thin layer of connective tissue, covered generally with simple cuboidal 

 epithelium. In places the epithelial cells may be flat, or tall with nuclei 

 in two rows. Cilia are sometimes widely distributed and are usually to 

 be found on the floor of the cavity. In its anterior part, small alveolar 

 mucous glands occur very sparingly. Capillaries form wide-meshed net- 

 works in the connective tissue, and lymphatic vessels are found in the 

 periosteum. 



The auditory tube includes an osseous part toward the tympanum, and 

 a cartilaginous part toward the pharynx. Its mucosa consists of fibrillar 

 connective tissue, together with a ciliated columnar epithelium which 



Cartilage 



Cartilage. 



M ucosa of the 

 pharynx. 



Glands. 



Glands. ---ZIZ~ 



FIG. 483. CROSS SECTION OF THE CARTILAGINOUS PART OF THE AUDITORY TUBE. 

 (Bohm and von Davidoff.) 



X 12. 



becomes stratified as it approaches the pharynx. The stroke of the cilia 

 is toward the pharyngeal orifice. In the osseous portion, the mucosa is 

 without glands and very thin; it adheres closely to the surrounding bone. 

 Along its floor there are pockets containing air, the cellules pneumatics. 

 In the cartilaginous part the mucosa is thicker; near the pharynx it con- 

 tains many mucous glands (Fig. 483). Lymphocytes are abundant in 

 the surrounding connective tissue, forming nodules near the end of the 

 tube, which blend with the pharyngeal tonsil. The cartilage, which only 

 partly surrounds the auditory tube, is hyaline near its junction with the 

 bone of the osseous portion; it may contain here and there coarse fibers 

 which are not elastic. Toward the pharynx the matrix contains thick 

 nets of elastic tissue, and the cartilage is consequently elastic. 



