THE RESPIRATORY TRACT. 255 



from that mass of connective tissue from which the vocal cords 

 take their origin. After prolonged maceration in some alka- 

 line solution, this cartilage can be separated into three parts 

 two lateral and an anterior or median. 



The arytenoids are not composed exclusively of hyaline 

 cartilage. The vocal process, as already mentioned, presents a 

 yellow reticulated structure, the fibres of which are continuous 

 with those of the true vocal cords. The apex has also a re- 

 ticular structure when there is no joint between it and the 

 cartilage of Santorini. The elastic tissue is then continuous 

 with that which connects it with the corniculum. A hori- 

 zontal section through the arytenoid at the level of the vocal 

 process shows the reticular structure of the process, the hya- 

 line character of the body of the cartilage, and the gradual 

 transition from one to the other. 



The three cartilages already described are subject to calci- 

 fication and partial ossification. This occurs more frequently 

 and at an earlier age in the male than in the female. It also 

 begins at a later date in those who have been castrated. It 

 makes its first appearance at the points of muscular attach- 

 ment. As the cartilages undergo calcification they increase in 

 size, so that the calcified larynx of old age is larger than that 

 of the young adult. The matrix also splits up into a fibrous 

 texture, not affected by acetic acid. 



The cornicula laryngis or cartilages of Santorini and the 

 cuneiform cartilages of Wrisberg, as well as the sesamoid 

 cartilages (when they exist) are of the reticulated variety. 

 The cartilago triticea is hyaline and prone to calcification. 



The epiglottis consists of reticular cartilage. On transverse 

 section, however, the intercellular substance is seen to be a 

 spongy elastic substance, granular on section ; at the periphery 

 yellow fibres are present. The elastic cartilage should be ex- 

 amined with a high power. 



The mucous membrane of the larynx varies in its structure 

 in different situations. On the laryngeal surface of the epi- 

 glottis it is thin. 



The epithelium in the upper half is in several layers. The 

 deepest cells are somewhat columnar or pyramidal in form, 

 while the superficial ones are flat. The lower half is covered by 

 a stratified, columnar, ciliated epithelium. The epithelium rests 

 upon a thin, apparently structureless basement-membrane. 



