CARCINOMA OF THE LAEYNX. 307 



to it from neighbouring parts. Owing to the virtual isolation of 

 the laryngeal lymphatic system, laryngeal neoplasms never arise 

 as metastatic deposits. 



From a clinical standpoint carcinomata of the larynx are 

 divided into two classes, extrinsic and intrinsic. The extrinsic 

 varieties may arise on the posterior surface of the cricoid carti- 

 lage, in the arytenoid region, the aryteno-epiglottidean folds or 

 on the posterior surface of the epiglottis. Intrinsic carcinomata 

 usually arise from the posterior parts of the true cords, but may 

 spring from the false cords, the ventricles of the larynx, or the 

 subglottic region. 



The commonest site of extrinsic carcinoma is the back of the 

 cricoid cartilage, whilst intrinsic cancer, as just mentioned, 

 usually arises from the vocal cords. Both these localities may 

 be considered subject to friction and irritation, the back of the 

 cricoid during deglutition, and the vocal cords during phonation. 



The anatomical justification for the classification given above 

 is found in the arrangement of the laryngeal lymphatics. The 

 supraglottic region, the site of extrinsic carcinoma, is provided 

 with a rich lymphatic network which is densest where the 

 mucous membrane is thickest, and is in some degree continuous 

 with the lymphatics of the pharynx and back of the tongue. 

 The lymphatics of the glottic and subglottic regions, positions in 

 which intrinsic carcinomata originate, are more scanty, and in 

 the true cords are, for all practical purposes, non-existent. The 

 subglottic network communicates in some measure with that of 

 the trachea. The lymphatics of one-half of the larynx com- 

 municate freely across the posterior median line, but not at all 

 freely anteriorly. Extrinsic cancer, guided by the course of the 

 lymphatics, tends to spread towards the upper parts of the 

 larynx and the pharyngo-laryngeal region. It may perforate the 

 posterior part of the thyro-hyoid membrane near the exit of the 

 lymphatic trunks. Early glandular enlargement is the rule, and 

 the first to suffer is often a small gland on the thyro-hyoid 

 membrane. Extension downwards in the region of the vocal 

 cords is very slow. 



202 



