FRAMEWORK OF THE LARYNX. 35 



of the cartilage itself, but of the means by which the segments 

 are connected together. 



The cartilage of the trachea in Man partly belongs to the 

 type of hyaline, partly to that of fibre-cartilage, and in the 

 earlier stages of development possesses a tolerably active meta- 

 morphosis of tissue, the demands for which are supplied by 

 appropriate bloodvessels, and regulated by nerves. At some 

 few points the perichondrium gives off processes that penetrate 

 into the substance of the cartilage, and consist of delicate 

 connective tissue, with numerous fusiform cells, between which 

 many vessels of different size may be distinguished, as well as 

 a few nerve fibres. In the adult this direct connection between 

 the cartilage and the vessels of the perichondrium either dis- 

 appears altogether or becomes materially diminished. 



With the advance of age the hyaline cartilage undergoes 

 ossification, the change commencing usually at the age of forty 

 years, though exceptionally much earlier, as at twenty. The 

 process begins with the simple deposit of calcareous salts in 

 the matrix, and spreads with tolerable uniformity from certain 

 points of ossification. The limits of the ossification are conse- 

 quently not very sharply defined. There then occurs a scattered 

 punctiform precipitate in the matrix of the cartilage^ which 

 becomes constantly more and more dense, and ultimately blends 

 with the uniformly calcified matrix. Near the margin of the 

 ossified portion the cartilage cells appear still unaltered ; but at 

 a little distance from the margin, in the part which has been 

 for some time ossified, they are characterized by numerous 

 processes, giving them a stellate form, and they then present 

 no points of difference from ordinary bone corpuscles. The 

 fibro-cartilages, as a general rule, undergo no ossification with 

 advancing age ; an exception occurs, however, in the case of 

 the arytenoid cartilages of the Dog, which become ossified. 



To the series of pure fibro-cartilages belong the epiglottis, 

 the cartilages of Santorini, of Wrisberg, and the inconstant 

 sesamoid cartilages; to the pure hyaline belong the thyroid 

 and cricoid cartilages, and the corpusculum triticeum ; whilst; 

 lastly, the arytenoid cartilages appear to be partly hyaline and 

 partly fibrous. 



The cartilage of the epiglottis presents numerous excava- 



D 2 



