ARTICULAR CARTILAGES. 



343 



Fig. 222. 



to the surface of the latter. (Fig. 222.) Neither the articular carti- 

 lages nor the fibro-cartilages of circumference contain either nerves 

 or vessels, though the vessels of the synovial membranes sometimes 

 intrude upon them at their borders. 



Dr. Leidy, of Philadelphia, has also 

 observed numerous minute lacunae in 

 articular cartilages. These are lenticu- 

 lar in outline, y^^ to ^y 1 ^ of an inch 

 in length, and most abundant in the 

 deepest layer of the cartilage, and de- 

 crease in number towards its free sur- 

 face. Another peculiarity, also de- 

 scribed by Dr. Leidy, is the penetra- 

 tion of the structure of the articular 

 cartilage by fibres or columns of bone. 

 These fibres are compressed and cylin- 

 drical in shape, and present an ellip- 

 tical outline on a transverse section. 

 They are not numerous, are concen- 

 trically laminated, and present a radi- 

 ated appearance, not very unlike an 

 Haversian rod ; but neither the Haver- 

 sian canal, nor the lacunae and pores, 

 are to be seen. 



The condition of the bone beneath 

 the articular cartilages is peculiar, con- 

 sisting, in almost all joints, of a layer 

 of incompletely formed osseous tissue. Articular cartilage of a human meta . 



This layer is 3^ tO ^ (average y^) car Pal bone, cut perpendicularly, a. Most 



n i xi i -i * 11 i superficial, flattened cartilage-cells. 6. 



Ot an inch thick, and IS a yellowish, Middle round cells, c. Innermost cells, 



mOStly fibrOUS, hard, and truly OSSified dis P sed perpendicularly in small rows. 



. . , d. Outermost layer of the bone, with os- 



matrix; containing, however, not a sified fibrous matrix, and thick-waned 



trace Of Haversian Canals Or medul- artilage-cells, in this instance appearing 



dark from their containing air. e. True 



lary cavities, nor any perfectly formed bone-substance. /. End of the cancein 

 lacunas. Instead, however, of these, of * he e h ? ses - * One of the cancelli - 



' rt Magnified 90 diameters. (Killiker.) 



are found roundish or elongated cor- 

 puscles, aggregated into little masses or rows 5 <>W to jJ T of an inch 

 long, and T? Vo to 3<y<nr of an inch broad. These give thin sections 

 of the bone a perfectly opaque aspect; and are really thick- walled 

 cartilage-cells, retaining their contents (fat and nuclei), occasionally 



