THE LARYNX. 



1823 



contact, they close the glottis and prevent the entrance of air, but from their shape 

 they seem unfitted to prevent its exit. This, according to the general teaching, is 

 accomplished by the valvular action of the false cords, to which the ventricles con- 

 tribute, but it is not clear that they contain the musculature necessary for such action. 



The infraglottic region (conus elasticus) expands laterally beneath the true 

 cords so as to become practically circular before reaching the lower border of the 

 cricoid. The little fossa beneath the arytenoid cartilages is the upper part of this 

 region, which is broadest between them. 



The mucous membrane of the larynx is in parts thin and tightly bound 

 down to the cartilages beneath it, and elsewhere thick, with much subjacent areolar 

 tissue. It is very intimately connected to the free part of the epiglottis and to all of 

 its intralaryngeal surface, but less so to the anterior part near the tongue. It is closely 

 applied to the arytenoids and also to the lower part of the cricoid. It is thin and 

 adheres very tightly to the true vocal cords along the ligament. In the ary epiglottic 



Fig. 1552. 



Glands 



Vocal cords — \ '  if/i 



i;. I.l 'I 



Thyro-arytenoid — I — fjvm 

 muscle ' «?[!' 



Ventricle ;' /"■>., ', 



Fibres of thyro- 

 arytenoid perhaps 

 inserted into vocal \^ 

 process 



Lateral crico- — -^ 

 arytenoid muscle 



Glands 



-, /'.'■ 



J' ' 

 '-^J False vocal cord 



r^ Ventricle 



Vocal process of 



y. arytenoid cartilage 



Cricoid cartilage 



Frontal section of larynx through vocal processes of arytenoid cartilages. X 3. 



folds it is lax and redundant. Beginning at the base of the epiglottis, the epithelium 

 covering the mucous membrane is of the stratified ciliated columnar type throughout 

 the larynx, with the exception of that over the vocal cords, false as well as true, 

 which abruptly changes to stratified squamous. Mucus-secreting goblet-cells occur 

 in varying profusion among the columnar elements. The superficial layers of the 

 fibro-elastic stroma of the mucous membrane contain many lymphocytes, which in 

 places are so numerous that the tunica propria resembles lymphoid tissue. 



The glands are very general. They occupy pits in the epiglottis, are very numer- 

 ous and large in the false cords, and plentiful in the walls of the ventricles. They do 

 not occur on the upper surface of the true cords within 3 or 4 mm. of the free edges, 

 but in the infraglottic region form nearly a continuous shallow layer to within 2 or 3 

 mm. of the free edge of the vocal cord. The laryngeal glands are tubulo-alveolar in 

 form and mixed mucous in type, in addition to the mucus-producing cells containing 

 groups of serous elements. 



Lymphoid tissue, as distinct nodules, is occasionally observed on the posterior 



