344 



THE TISSUES. 



presenting indications of pores, and being perhaps also partly calci- 

 fied. In other cases they are, in fact, undeveloped lacunae. This 

 layer is bounded towards the cartilage by a straight line, and towards 

 the bone by a sinuous contour. It occurs in every articulation, 

 except that of the lower jaw, and those on the os hyoides. (Kolliker.) 

 (Fig. 222.) 



In pathological states, the articular cartilages sometimes assume a 

 fibrous structure, a change often attended by an increase of thick- 

 ness. These fibres are sometimes half an inch in length. (Cruveilhier.) 

 Sometimes they wear away rapidly, or even entirely disappear, leav- 

 ing the bones bare. They may also be attacked by ulceration ; this 

 penetrating to the bone, or commencing next to it and extending 

 towards the free surface. 



The Synovial Membranes. 



The synovial membranes are not closed cavities, as generally de- 

 scribed; but merely of the form of rings, or short tubes, whose two 

 open ends or borders are attached to the circumference of the articu- 

 lar surfaces of the bones, and thus connect them together. They 

 are delicate transparent membranes, but are often invested exter- 

 nally by the capsular or other ligaments of joints, from which they 

 are with difficulty separated. 



The precise relations of the synovial mem- 

 branes are as follows: They are attached 

 simply to the border of the articular surface, 

 and either thrown across directly to the other 

 bone, or they may in the first place invest a 

 small surface of the first bone also, as well 

 as the cartilage, and then pass to the other 

 bone. (Fig. 223.) In either case, the syno- 

 vial membrane does not adhere directly to 

 the hard tissues underneath it ; but is more 

 or less closely connected with the periosteum 

 or the perichondrium. It finally terminates, 

 Diagram of a longitudinal sec- without any distinct margin, near the border 

 tion of a phaiangeai articuia- o f the articular cartilage, being inseparably 



tion ; partly after Arnold, a. _ . , . , , . 



Bones. 6. Articular cartilage. United With its perichondrium. 



c. Periosteum continuous with j n fa Q ^. i nt i ma t e structure, the synovial 



the perichondrium of the latter. 



d. Synovial membrane at the membranes COnSlSt -first, of a layer 01 COn- 

 edge of the cartilage, connected Censed areolar tissue, with vessels and 



at first with the perichondrium. 



e. its epithelium. (K'liiker.) nerves ; and, secondly, an epithelium. 



Fig. 223. 



