THE RESPIRATORY SYSTEM. 469 



more active and an increased quantity of mucus is formed. There is 

 desquamation of the superficial epithelial cells, while through emigra- 

 tion leucocytes may infiltrate the submucosa, and together with mucus 

 and desquamated epithelium form the exudate. There may be oedema 

 of the glottis. 



After death the congestion of the mucous membrane frequently dis- 

 appears altogether. 



Chronic Catarrhal Laryngitis. The surface of the mucous membrane is 

 dry or coated with muco-pus. The epithelium is thickened in some 

 places, thinned in others, or in places entirely destroyed. The submu- 

 cosa may be infiltrated with cells, diffusely thickened, or form little 

 papillary outgrowths; it may be thinned, or necrotic and ulcerated. 



The mucous glands may be swollen and prominent. The inflamma- 

 tion may extend to the perichondrium of the cartilages, which may 

 become necrotic. In chronic laryngitis there may be a more or less 

 diffuse thickening of the epithelium, often associated with an hyperpla- 

 sia of the submucous tissue. This is called pachydermia diffusa. A sim- 



FIG. >'J.-LOCALIZED HYPERPLASIA OF THE EPITHELIUM AND SCBMUCOUS CONNECTIVE TISSUE OF THE 

 FALSE VOCAL CORDS. 



The section shows a portion of a small rough wart-like or papillary growth. 



ilar process, if localized, may lead to larger and smaller wart-like 

 excrescences pachydermia verntcosa (Fig. 259). 



Croupous Laryngitis occurs most frequently as the characteristic local 

 lesion in diphtheria, of which the Bacillus diphtherias is the excitant (see 

 page 259). It may, however, be incited by the Streptococcus pyogenes 

 and other bacteria, and not infrequently accompanies other infectious dis- 

 eases, scarlatina, typhoid fever, and other exanthemata (see page 209). 

 The false membrane may be continuous with a similar structure in the 

 pharynx, and it may extend down into the bronchi. 



Phlegmonous Laryngitis. Suppurative inflammation involving the 

 mucosa and submucosa is usually secondary to catarrhal, croupous, tuber- 

 culous, or syphilitic laryngitis ; or it may be associated with pyaemia or 

 erysipelas, or it may follow mechanical injury from a foreign body. It 

 is not uncommon on the posterior surface of the epiglottis or in the ary- 

 epiglottidean folds, and may be associated with O2dema of the glottis. 



