112 STRUCTURE OF CARTILAGE. 



in another a layer which extends completely around the joint and is 

 then called a capsular ligament. All the ligaments of joints are com- 

 posed of that variety of fibrous tissue termed white fibrous tissue, but 

 in some situations ligaments are found which consist of yellow fibrous 

 tissue, for example, the ligamenta subflava of the arches of the verte- 

 bral column. Adipose tissue exists in variable quantity in relation 

 with joints, where it performs, among other offices, that of a valve or 

 spring, which occupies any vacant space that may be formed during 

 the movements of the joint, and effectually prevents the occurrence of 

 a vacuum in those cavities. This purpose of adipose tissue is exem- 

 plified in the cushion of fat at the bottom of the acetabulum and in 

 the similar cushion behind the ligamentum patellae. Synovial mem- 

 brane constitutes the beautiful smooth and polished lining of a joint, 

 and contains the fluid termed synovia by means of which the adapted 

 surfaces are enabled to move upon each other with the perfect ease 

 and freedom which are known to exist. 



CARTILAGE. In the structure of joints, cartilage serves the double 

 purpose of a connecting and separating medium. In the former capa- 

 city possessing great strength, and in the latter smoothness and elasti- 

 city. In reference to its intimate structure it admits of classification 

 into three kinds, true cartilage, reticular cartilage, and fibrous car- 

 tilage. 



Trm Cartilage is composed of a semi-transparent homogeneous sub- 

 stance (hyaline or vitreous substance) containing a number of minute 

 cells (cartilage corpuscles) dispersed at short intervals through its 



Fig. 47.* 



* A portion of articular cartilage from the head of the fibula. The section is 

 made vertically to the surface, and magnified 155 times. A. The appearance 

 and arrangement of the cells near to the bone. The irregular line to the right 

 is the boundary of the bone. u. A view of the same section, at about midway 

 between the bone and the free surface, c. A portion near the synovial surface ; 

 the line to the left is that of the syuovial boundary. 



