THE RESPIRATORY TRACT. 711 



Exner, there is no essential difference between the columnar and 

 the olfactory epithelia, which exhibit forms of transition, the 

 reticular layer at the bottom of the epithelia being destined for 

 their indirect connection with the terminal fibers of the olfac- 

 tory nerve. The tubular glands (Bowman), which occupy the 

 whole breadth of the mucosa, are said to be lined by columnar 

 epithelia. 



(2) The larynx is composed of a cartilaginous frame, which 

 serves for the attachment of the striped muscles and the mucosa 

 through the intervening perichondrium. Most of the cartilages 

 are hyaline, but freely intermixed with fibrous, especially in 

 the middle portion (see page 206, Fig. 79). The epiglottis, the 

 supra-arytenoid and cuneiform cartilages are composed of retic- 

 ular cartilage, and this variety is also, as a rule, found in the 

 processus vocales of the arytenoid cartilages. The cartilage of 

 the epiglottis is in several places divided by fibrous tracts, con- 

 taining a few blood-vessels, and in its laryngeal surface excava- 

 tions are seen for the reception of large mucous glands. 



The mucosa of the larynx is either uniformly composed of a 

 loose, fibrous connective tissue, or of dense fibrous tissue near 

 the surface (vocal bands), and loose submucous tissue in the 

 deeper portions. Both are freely supplied with elastic fibers, 

 which are especially developed in the mucosa of the vocal bands. 

 In the latter situation longitudinal bundles of smooth muscle- 

 fibers are intermixed with the connective tissue. The submucous 

 layer contains large quantities of lymph-tissue, more abundant 

 in children than in adults, although in the larynges of the latter 

 we find tissue of this kind in the mucosa covering the ventricles 

 and the ventricular folds. In addition, a varying amount of 

 fat-globules is also observed in the submucous tissue. 



The papillae of the mucosa of the larynx are very small, and 

 it is only at the glossal surface of the epiglottis and in the 

 region of the arytenoid cartilage that they are more marked. 

 Along the posterior wall of the larynx, and on the ventricular 

 folds, the mucosa is duplicated into elevations, which are often 

 mistaken for papillae. 



At the glossal surface of the epiglottis the epithelial cover is 

 broad and stratified, and supplied with formations similar to 

 gustatory buds. The stratified epithelium gradually decreases 

 in breadth after passing over the edge and the laryngeal surface 

 of the epiglottis. Toward the lower third of the latter it is 

 changed into ciliated columnar epithelium, which lines the 



