CARTILAGE. 267 



Structure. — On putting a slice of true cartilage under the mi- 

 croscope, it is seen to consist of a number of minute cells disseminated 

 through a vitreous substance. The cells are oval, oblong, or poly- 

 hedral in shape, and more or less flattened by packing. The mem- 

 brane forming the cell-wall is usually blended with the matrix, but 

 sometimes consists of concentric layers. White fibres usually en- 

 close the mass of cells, and even dip sometimes into those cells 

 more superficially placed. The cells or corpuscles are contained in 

 hollow cavities, called lacunae. Sometimes they do not entirely fill 

 up the lacunae, so that a vacant space is left. The corpuscles are 

 usually dispersed in groups, varying in size and form, through the 

 matrix ; the groups towards the surface of the cartilage are gene- 

 rally flattened conformably with the surface. In articular car- 

 tilage, the matrix in a thin section appears dim and presents a 

 granular aspect, the cells and nuclei of which are small. The pa- 

 rent-cells enclose two or three younger cells. The groups they 

 form are flattened near the surface, and lie parallel with it. In the 

 internal part of this cartilage the cells assume a linear direction, 

 and point towards the surface. Near its attached surface cartilage 

 blends with the bone, the cells and nuclei of which become sur- 

 rounded by little granular bodies, which seem to be the rudimen- 

 tary deposit of bone. In costal cartilage the cells are very large ; 

 they contain two or more nuclei, which are clear and transparent, 

 and some contain a few oil globules. The cells, internally situated, 

 form oblong groups, disposed in lines radiating to the circum- 

 ference. We observe a great quantity of intercellular tissue, in 

 the form of white fibrous structure, the fibres of which are parallel 

 and straight. 



Perichondrium (xspl, around, and %6v8pos;, cartilage), is a 

 white fibrous substance, which covers the external surface of all 

 cartilages, except those of the joints. In this membrane the blood- 

 vessels which supply the cartilage with blood, ramify. It is analo- 

 gous to the periosteum which covers the external surface of bones. 



Nerves. — No nerves have been traced into any of the. car- 

 tilages ; they are destitute of sensation while free from inflam- 

 mation. 



Blood-vessels. — Cartilage is non-vascular; it receives its nou- 

 rishment from the bone and perichondrium by imbibition. The 

 law of endosmose coming into operation when the tissue is thick, 

 as in the costal cartilages, canals are formed through which the 

 vessels pass to supply the parts which are too far removed from 

 the perichondrium. In articular cartilages no vessels enter. When 

 cartilage is removed by mechanical means, or by absorption, it is 

 not regenerated, and when fractured, as in the ribs, there is no 

 reunion by cartilage, but by fibrous, or most frequently by osseous 

 deposition. 



