CARTILAGE 71 



Elastic Cartilage. Elastic cartilage occurs in the external ear, in 

 the auditory tube, in the epiglottis and in the cuneiform and corniculate 

 cartilages and the vocal processes of the arytenoid cartilages of the 

 larynx. It is essentially hyaline cartilage the matrix of which has 

 become permeated with delicate elastic fibers forming a dense interlacing 

 network. The large spheroidal cartilage cell lies in a lacuna bounded 

 by a capsule and surrounded by a layer of hyaline matrix free of elastic 

 fibers. The plates of elastic cartilage, like those of the hyaline variety, 

 are surrounded by a dense fibrous perichondrium. Neither blood-vessels, 

 nerves, nor lymphatics are distributed within the matrix of elastic car- 

 tilage. 



Fibrocartilage. This tissue forms the interarticulai cartilages of the 

 lower jaw, the clavicle, and the knee; composes the iutervertebral disks 

 and the other cartilaginous symphyses of 

 the body ; lines the tendon grooves of the 

 bones, and forms the glenoid ligament of 

 the shoulder and the cotyloid ligament 

 of the hip. Fibrocartilage is intermedi 

 ate in structure between hyaline carti 



lage and such very dense fibrous tissue FlG ' S^-FIBROCARTILAGE, SHOW- 



ING A GROUP OF OVAL CAR- 

 as occurs in the tendons of muscles. At TILAGE CELLS. 



the attached margins of the cartilaginous 



.... r rom the sermlunar cartilage of 



plates its tissue is continued by imper- the knee of man. Hematein and 



ceptible gradations into the surrounding eosin. X 550. 



fibrous connective tissues. Like the 



other forms of cartilage, this variety is also non- vascular and devoid of 



nerves. 



Microscopically, fibrocartilage differs from such dense white fibrous 

 tissue as is found in the ligaments and tendons, in that the meshes of 

 the dense fibrous tissue of fibrocartilage are everywhere permeated by a 

 hyaline matrix in which here and there are small groups of ovoid car- 

 tilage cells. Each cartilage cell is occasionally surrounded by a charac- 

 teristic, concentric, lamellar appearance of the adjacent matrix, the so- 

 called 'capsule/ Plates of fibrocartilage, unlike the other varieties, are 

 not surrounded by a perichondrium. 



A peculiar sort of connective tissue of eutodermal origin is found 

 in the nuclei pulposi of the invertebral disks. It is the sole adult 

 vestige of the embryonic axis, the notochord. According to Williams 

 (Amer. Jour. Anat., 8, 3, 1908), who carefully studied its cytomorphosis 

 in the pig, "It is primarily cellular and epithelial; later it becomes a 



