Dean D. Lewis 17T 



ELASTIC TISSUE OF INFERIOR ZONE. 



Coxus Elasticus (Luschka) : Liog. Crico-thyreo-aryt^exoidea 

 OF Krause ' AXD Leg. Cricotiiyreoideum Medium (Hexle). 



If a lamina of the thyroid cartilage and the subjacent muscle be re- 

 moved, a fan-shaped mass of elastic fibers will be seen, which passes from 

 the angle of the thyroid cartilage downward, backward and laterad 

 to be attached to the ascending upper border of the cricoid cartilage 

 and the inferior surface of the vocal process of the arytenoid cartilage. 

 This elastic membrane is the conus elasticus of Luschka. Sections at 

 various levels through it will be described. 



In frontal sections, made through the anterior part of the conus elasti- 

 cus, a dense network of elastic fibers arising from the upper border of 

 the cricoid cartilage, and passing cephalad and laterad to be attached to 

 the lower border of the thyroid cartilage, will be seen. The fibers com- 

 posing this network tend to pass vertically, anastomose freel}'', and some 

 of the fibers arise on each side of an indefinite median raphe. On both 

 sides these fibers are continuous with elastic fibers passing from the upper 

 border of the cricoid cartilage. The mass of elastic fibers occupying the 

 median line form the ligamentimi cricotiiyreoideum medium, and 

 are seen to be merely the anterior continuation of the conus elasticus, 

 as previously shown by His. This ligament is pierecd by the crico- 

 thyroid artery, and the arrangement of some of its component fibers 

 about a median raphe suggests that functionally it is divided into sym- 

 metrical parts. (See Fig. 1.) 



In frontal sections made through the middle of the conus elasticus, 

 elastic fibers, few in number, and small in size, are seen arising from the 

 upper border of the cricoid cartilage, and passing cephalad and mediad 

 to reach the ligamentum vocale. These fibers, increasing constantly in 

 number and size as they ascend, form a gentle curve, the convexity of 

 which is directed mediad, being separated in the subglottic region from 

 the subepithelial elastic layer, by numerous glands, and loose connective 

 tissue, which favors the development of oedema at this point. The con- 

 cavity is occupied by the musculus vocalis. The fibers below are obliquely 

 arranged, and only as the plica vocalis is approached do they tend to 

 become sagittally directed and parallel. (See Fig. 2.) 



Sections made through the posterior part show that the conus l)ecomes 

 shorter and approaches nearer the median line. The fibers are more 

 nearly vertical in arrangement, passing up to the inferior surface of the 



'Krause: Handb. der menschlichen Anatomie. Hannover, 1879. 



