CARTILAGE. BONE. TEETH. 



Relations be- 

 tween cartilage 

 and bone. 



Articular carti- 

 lage. 



Distribution. 



able quantity, and plasm atic cells. These latter exist 

 in greatest number in the deepest portions of the 

 membrane, and it is to be noticed that those in imme- 

 diate contact with the surface of the cartilage are not 

 distinguishable in appearance from cartilage cells 

 (PL V. fig. II). Are we not justified in concluding 

 from this fact that the growth of cartilage is effected 

 by the transformation of these plasmatic cells of its 

 perichondrium ? 



Cartilages are united to bones by immediate con- 

 tact or apposition ; there is no substance or tissue 

 interposed between them. Their opposed surfaces 

 are rough, and their minute elevations and depressions 

 fit into each other accurately. 



It was supposed for a long time that the free sur- 

 faces of articular cartilage were invested with syno- 

 vial membrane. Careful examination of the surface 

 of the cartilage demonstrates, however, that within 

 the cavity of a joint it is entirely naked ; it is not 

 even covered by the epithelial layer of the synovial 

 membrane. It is incorrect therefore to describe 

 synovial membranes as shut sacs, and as lining the 

 whole interior surface of an articular cavity. A syno- 

 vial membrane simply covers the internal surface of 

 -the capsular expansion which surrounds the joint, or, 

 to be more exact, it is nothing more than the capsule 

 of the joint covered internally by a layer of epithe- 

 lium. It is to be understood, however, that those 

 ligaments which present a free surface in the cavity 

 of a joint are also invested by epithelium. 



Under the head of true cartilage are included: 

 the cartilaginous skeleton of the foetus, the costal car- 



