THE OSSEOUS SYSTEM. 



285 



which are arranged parallel with the principal direction of the elastic 

 fibres. According to Todd and Bow- 

 man (p. 72), the stylo-hyoid, and 

 internal lateral ligament of the lower 

 jaw, are, also, chiefly composed of 

 strong elastic fibres. 



3. By cartilage, syncJwndrosis. 

 This mode of connection is effected 

 either by cartilage alone, or -asso- 

 ciated with fibro-cartilaginous and 

 fibrous tissue. The former condition 

 is observed in the adult, only between 

 the ribs and sternum, where, how- 

 ever, properly speaking, a true syn- 

 chondrosis exists only in the case of 

 the first rib, the rest, from the second 

 to the seventh, being connected with 

 the sternum at the anterior extre- 

 mity by articulation ; whilst the 

 false ribs are either free at the ex- 

 tremity, or are incurved one beneath 

 the other. In the symphysis pubis, 

 sacro-iliac synchondrosis, and the 

 Junctions of the bodies of the verte- 

 brce, the surfaces of the bones are 

 covered immediately by a layer of 

 true cartilage, which, in the two 

 former situations, is directly connected with the opposite layer, and in the 

 latter by means of a fibro-cartilaginous tissue, and is externally encircled 

 by fibro-cartilaginous, and fibrous, concentric layers. In the two former 

 of these instances, there is, not unfrequently, a cavity in the interior of 

 the connecting substance, so that the sacro-iliac sychondrosis, in particu- 

 lar, may also be regarded as a sort of articulation (Zaglas). 



The intervertebral ligaments, or ligamentous discs, of the bodies of 

 the vertebrae, consist, 1, of exterior concentric layers of fibro-cartilage, 

 and whitish connective tissue ; 2, of a central, principally fibro-cartila- 

 ginous substance ; and 3, of two cartilaginous layers applied immedi- 

 ately upon the bones. 



The concentric lamellae consist of alternate layers of connective tissue 

 and of fibro-cartilage, which latter, even in fresh transverse sections, 



FIG. 121. ./, a transverse section through a portion of the ligamentum nuchce of the Ox, 

 magnified 350 diameters, and treated with soda: a, connective tissue, apparently homoge- 

 neous; 6, transverse section of the elastic fibres (O004-0 01 of a line in diameter). J5, elastic 

 fibres; a, from a human lig. subflavum, together with some connective tissue, 6, between 

 them, magnified 450 diameters. 



