36 THE LARYNX. AND TRACHEA, BY E. VERSON. 



tions and fossae on its posterior or inferior surface, which often 

 even penetrate through its whole thickness, and then usually 

 permit the passage of vessels and small nerves. The shal- 

 lower depressions are occupied by fat cells or acinous glands, 

 of which the latter are collectively situated on the posterior 

 surface of the organ. The perichondrium, of course, follows 

 all the hollows and inequalities of the cartilage. The epiglottis 

 ossifies only in reptiles and birds, in which it is in intimate 

 relation with the thyroid cartilage. 



The thyroid cartilage exhibits a hyaline structure in 

 general, though there are a few points where fibres appear 

 between the cartilage cells. This especially occurs at the 

 borders from which elastic bands of attachment extend to the 

 hyoid bone and to the cricoid cartilage, and to a still greater 

 extent in the re-entering angle at the level of the true vocal 

 cords, the most external fibres of which run deeply into the 

 cartilage, and to a certain extent divide it into three segments 

 a median, situated between the two vocal cords (lamina 

 mediana, Halbertsma), and two lateral. In the newly born 

 child another condition is exhibited, a similar segmentation into 

 those parts being indicated, but only by the circumstance that, 

 as in the adult, the more closely arranged cartilage cells of the 

 median portion appear bounded on each side by a line, the 

 concavity of which is directed outwards, of more scattered and 

 uniform-sized cells. A complete tri-partition of the thyroid 

 cartilage occurs only in birds. Lastly, fibrous bands may be 

 found in the central portions of the thyroid cartilage of young 

 animals, partly alone, and partly constituting a support for 

 bloodvessels. 



In regard to the cartilages of Wrisberg, it is well known 

 that they sometimes break up into three or more rounded 

 masses, which are sometimes arranged vertically one over the 

 other, and sometimes on the same horizontal plane. The peri- 

 chondrium investing the several nodules is elongated into 

 bands that decussate with each other, so as to leave spaces 

 occupied by acinous glands. 



The cartilage of Santorini (c. corniculata) appears to be 

 separated from the arytenoid cartilage only by a process of the 

 perichondrium, which is distinguished from that investing 



