CARTILAGE. 



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often stains with greater intensity, thereby producing the appearances known as 

 the cell-areas. The lacunae of hyahne cartilage are homologous with the lymph- 

 spaces of other dense forms of connective tissue ; although canals establishing com- 

 munication between the adjacent lacunae are not demonstrable in the tissues of 

 the higher vertebrates, it is not improbable that minute interfascicular passages 

 exist which facilitate the access of nutritive fluids to the cells enclosed within the 

 lacunae. 



The free surface of cartilage is covered by an envelope of dense connective 

 tissue, the perichondrium ; the latter consists of an external fibrous layer of dense 

 fibro-elastic tissue and an inner looser stratum or chondrogenetic layer, containing 

 numerous connective-tissue cells. These are arranged in rows parallel to the sur- 

 face of the cartilage and, during the growth of the tissue, gradually assume the 

 characteristics of the cartilage-cells, being at first spindle-shaped and later ovoid 

 and spherical. The young cartilage-cells thus formed become gradually separated 

 by more extensive tracts of the newly deposited intercellular matrix ; as the groups of 

 cells originating from the division of the original occupant of the lacuna recede from 

 the perichondrial surface, they 



lose their primary parallel dis- Fig. iio. 



position and become irregu- 

 larly arranged and still further 

 separated. Those portions of 

 the ground-substance most re- 

 mote from the perichondrium 

 at times appear granular, this 

 feature being intensified when, 

 as in aged subjects, a deposition 

 of calcareous matter takes place 

 in these situations. 



In articular cartilage the su- 

 perficial zone contains sparsely 

 distributed groups of small cells 

 arranged parallel to the free 

 surface ; in the deeper strata 

 these groups are replaced by 

 elongated rows of larger ele- 

 ments lying perpendicular to 

 the articular surface. This 

 columnar disposition of the car- 

 tilage-cells is particularly evi- 

 dent towards the underlying 

 zone of calcified matrix. 



The blood-vessels of normal 

 cartilage are usually limited to 

 the periphery, within the perichondrium or the associated synovial membranes ; the 

 nutrition of the cartilage is maintained by imbibition of the fluids through the matrix 

 into lacunae, the existence of minute interfascicular canals being not impossible. 

 In the thicker masses of the tissue, as in the cartilages of the ribs, nutrient canals 

 exist in those portions most remote from the perichondrium ; these spaces contain a 

 small amount of areolar tissue supporting the blood-vessels, which are, however, 

 limited to the channels, the nutrition of the cartilage tissue being effected here, as at 

 the periphery, by absorption through the matrix. 



Nerves have never been demonstrated within the cartilages, which fact explains 

 the conspicuous insensibility of these tissues so well adapted to the friction, concus- 

 sion, and compression incident to their function. 



Elastic cartilage, called 2\'so yellow elastic ox reticular c2s\jA2.^q. (Fig. iii), 

 has a limited distribution, occurring principally in the cartilages of the external ear, 

 part of the Eustachian tube, the epiglottis, the cartilages of Wrisberg and of San- 

 torini, and part of the arytenoid cartilages of the larynx. In its physical properties 

 this variety differs markedly from hyaline cartilage, as it is dull yellowish in color 



6 



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Perichondrium 



Young cartilage- 

 cells 



Group of older 

 cells. 



Cartilage-cells 



Lacuna contain- 

 ing nest of 

 cells 



Empty lacuna 

 surrounded by 

 hvaliiie matrix 



Transverse section of peripheral portion of costal cartilage, X 250. 



