THE OSSEOUS SYSTEM. 313 



extremity by articulations ; whilst the false ribs are cither 

 free at the extremity, or are incurved one beneath the other. 

 In the symphysis pubis, sacro-ihac synchondrosis, and the 

 junctions of the bodies of the vertebra, 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. Tn the two former 

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

 interior of the connecting substance, so that the sacro-iliac 

 synchondrosis, in particular, may also be regarded as a sort of 

 articulation (Zaglas). 



[The intervertebral ligaments, or ligamentous discs, of the 

 bodies of the vertebra?, consist, 1, of exterior concentric layers 

 of fibro-cartilage, and whitish connective tissue; 2, of a 

 central, principally fibro-cartilaginous substance ; and, 3, of 

 two cartilaginous layers applied immediately upon the bones. 



The concentric lamella consist of alternate layers of con- 

 nective tissue and of fibro-cartilage, which latter, even in 

 fresh transverse sections, may be recognised as dull yellow 

 streaks, which become hard and transparent in water. The 

 fibro-cartilage, on microscopic examination, presents minute, 

 elongated cartilage cells, disposed serially in a fibrous tissue, 

 differing from connective tissue in its greater rigidity, the 

 absence of distinct fibrils, its great resistance to alkalies and 

 acetic acid, and the total absence of elastic fibres. 



The whitish layers of the outer laminae, although their 

 fibrils are rather more rigid than those of the common liga- 

 ments and tendons, are less easily separated, and present 

 but few fusiform cells, and frequently no elastic fibres what- 

 ever among them, must nevertheless, at present, be regarded 

 as composed of connective tissue. These laminae are from 

 i to I'" and more in thickness, and form entire circles or 

 segments of such, which, alternating with the somewhat 

 thinner, and also frequently incomplete, rings of fibro-carti- 

 lage, with which they are closely connected, together with the 

 latter constitute the larger half of the intervertebral ligaments. 

 The general direction of the fibres of both sets of laminae is 



