CONNECTIVE TISSUES CARTILAGE. 



09 



other by an intervening deposit of that substance, which holds to them very 

 much the same relation that the gelatinous substance, copiously interposed 

 between the so-called "cells" of seaweeds, holds to those elementary parts. 

 In both cases, it is to be borne in mind that the intervening substance 



mm^-M ;- v. ----v^ 



Uv / O / "--: -.s~--: '- 



x v. ,.-,;^^ ^> d 



pKfj/ f* T. ^y-r^'r .{K \ f L ' ' \\ x^r-V; 

 ^>^ r r'./lXj^^ -ffi \ ~^^: ?* -~^J ./ ^-. 



FIG. 30. 





Section of Branchial Cartilage of Tadpole: a, group of 

 four cells, separating from each other; 6, pair of cells in 

 apposition; c, c, nuclei of cartilage-cells; (/, cavity con- 

 taining three cells. 



Elementary part, from Cartilage of 

 Frog, treated with carmine, show- 

 ing successive stages of con version of 

 germinal matter into matrix. 



represents the cell-wall of such cells as have a distinct limitary membrane, 

 but that the essential constituent of the cell is the segment of protoplasmic 

 substance, which is thus isolated. Ordinary articular cartilage is thickest 

 where the pressure is greatest, and the cells are found to be somewhat flat- 

 tened near the free surface, irregularly distributed in sets of from eight or 

 more near the centre, and perpendicularly placed in that part which lies 

 nearest the bone. 



The nutrition of cartilage, when it attains considerable thickness, is pro- 

 vided for by the passage of a few large vessels through channels in its sub- 

 stance, that are lined throughout by prolongation of the perichondriurn. 

 Beneath the articular cartilage the vessels of the bone form loops, the bight 

 of which is dilated into an enlargement, or sinus, which must cause a re- 

 tardation in the current of blood. Mr. Banvell ' has described a peculiar 

 arrangement bv which he believes the nutrition of articular cartilage is 



I. O 



maintained. This consists of an osseous lamella intervening between the 

 cartilage and the shaft of the bone, penetrated, like the dentine of the teeth, 

 with numerous fine canaliculi, running, in a wavy course, parallel to one 

 another and perpendicular to the surface. Through these the nutritive ma- 

 terials are conveyed to the cartilage from the above-named sinuses. The 

 costal, and most of the fibro-cartilages, are invested by a firm layer of con- 

 nective tissue, termed the perichondriurn. Though the two tissues may be 

 separated by prolonged maceration, they are structurally continuous with 

 one another. JSTo nerves or lymphatics have been hitherto traced into the 

 substance of cartilage, and it appears to be nearly insensible; hence the ex- 

 quisite pain accompanying ulceration of joints may probably be referred to 

 irritation of the nerves supplying the subjacent bone. The chemical com- 

 position of cartilage has not been accurately determined. On drying it 

 loses about 70 per cent, of water; on being subjected to prolonged coction 

 in water it yields choudriu, a substance that gelatinizes on cooling, and gen- 

 erally resembles gelatin, except that it is precipitated by acetic acid. The 

 organic basis from which the chondriu is derived constitutes about 80 per 



1 British and Foreign Med.-Chir. Kev., 1859, p. 489. 



