OF CARTILAGE. i; 



thickened. These cell-walls lie either in close contact, or have 

 only a trace of intercellular substance between them, or there 

 is sufficient of that material to entirely prevent the contact of 

 the different cells. Their walls, which are originally formed 

 of a very thin membrane, become thickened. The cavities of 

 the cells with thickened walls which are seen in the centre of 

 the branchial ray, are smaller than those of the cells which lie 

 nearer the surface, the walls of which arc less dense ; but, 

 whether this is produced by a thickening of the cell-wall taking 

 place from without inwards, or whether rather the cells were not 

 smaller in their original formation, is a matter of uncertainty. 

 No deposition of strata, nor any distinction from the primordial 

 cell -membrane, can be recognized in these thickenings of the 

 walls. The condensed cell-walls at length coalesce either with 

 each other, or with the intercellular substance, to form one 

 homogeneous mass, in which only the cell-cavities remain per- 

 ceptible, presenting the appearance of small distinct excavations 

 filled with a transparent substance ; these cell-cavities are the 

 cartilage-corpuscles. 



In the foregoing description no error can arise from the 

 great variety in form which the cartilage-corpuscles frequently 

 present ; for, on examining the branchial rays of a very large 

 pike, the gradual transition may be traced, from the thin- 

 walled almost globular cells to the most varied forms, in which 

 the remains of the cell-cavities are so much extended in length 

 as to give to the cartilage almost a fibrous appearance. 



The same extremely simple process of formation (modified, 

 however, in some important respects) is presented in all carti- 

 lages. These modifications, the fundamental type of which is 

 already pointed out in the cartilages of the branchial rays of 

 fishes above described, depend chiefly upon the share relatively 

 contributed by the thickened cell-walls, or the intercellular sub- 

 stance, to form the intermediate substance of the cell-cavities, 

 or cartilage-corpuscles. We have seen that this intermediate 

 substance was formed almost entirely of the thickened cell- 

 walls, with but a minimum amount of intercellular substance, 

 in the centre of the branchial rays of fishes, whilst at their base, 

 that is, in the earliest formed cartilage, the intercellular sub- 

 stance preponderated, and the less dense cell-walls contributed 

 less to the formation of the true substance of the cartilage. 



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