346 THE TISSUES. 



knee-joint). In intimate structure they do not differ from other 

 fibro-cartilages ; except that the car til age- cells are smaller and more 

 abundant in the deep, and less so in the superficial portions (p. 

 314). In old persons, they lose their distinct fibrous structure, and 

 assume a yellow or brownish color. 



The inter-articular ligaments, so called, must also be classified 

 with the preceding fibro-cartilages. They are not covered by sy- 

 novial membrane; nor even by an epithelium, except for a small 

 extent at their attached borders (e. g. ligamentum teres, &c.). 



Connection of Tendons and Ligaments with the Bones. 

 Tendons and ligaments are generally inserted into the periosteum. 

 Both are, however, in some instances inserted into the bone itself; 

 there being no trace of periosteum intervening. This is the case 

 with the tendons of the quadriceps femoris, pectoralis major, del- 

 toid, latissimus dorsi, psoas-iliac, glutasi, the tendo-Achillis, &c., and 

 the ligaments, mentioned on page 342, 2. In these cases the fasciculi 

 of the tendon rest at an acute or a right angle on the surface of the 

 bone, and become attached to all the elevations and depressions of 

 its surface. Close to the bones, the tendons frequently also con- 

 tain delicate cartilage-cells. They also, in exceptional cases, be- 

 come entirely incrusted with calcareous salts in the form of granules, 

 next the bone. Fig. 224 shows the peculiarities just mentioned. 



The general structure of the proper joints or movable articula- 

 tions (diarthroses) may be gathered from what has preceded. Each 

 diarthrodial articulation contains the following elements: 



1. The articular cartilages, covering the extremities of the bones, 

 described on page 343. 



2. The synovial membrane, secreting the synovial fluid (p. 344). 



3. In some instances, inter-articular fibro-cartilages (p. 345). 



4. Ligaments of various forms ; inter-articular and circumferen- 

 tial (pp. 346 and 342). 



The amphiarthroses, or symphyses, have a simpler structure. Here 

 the connection of the bones is by cartilage alone, or associated with 

 fibro-cartilage and white fibrous tissue. In the symphysis pubis, 

 sacro-iliac synchondrosis, and the articulations of the bodies of the 

 vertebrae, the surfaces of the bones are directly covered by a layer 

 of true cartilage; and which in the first two situations, is directly 

 connected with the opposite layer, and in the last, by means of fibro- 

 cartilage and white fibrous tissue in consecutive layers. In the 



