CARTILAGE. 315 



The relative amount of these two elements varies much in differ- 

 ent cartilages; either element alone also sometimes constituting 

 almost the whole mass. 



1. Cartilage -cells present no peculiarities in form, being rounded 

 or elongated, flattened, or fusiform, and very rarely stellate, as in 

 enchondrorna, and in cuttle-fishes and sharks. From 1 to 4 (or 

 even 20 to 30) cells exist together in a single cavity 1 in the inter- 

 cellular substance; and sometimes they are arranged in regular rows, 

 as in cartilages in which bone is about to be developed. (Fig. 225.) 



The cell-walls are usually thick, and frequently are invested by 

 concentric laminae. They are not dissolved by boiling, and long 

 resist alkalies and acids; thus resembling the elastic but not the 

 collagenous tissue (p. 282). 



The contents are clear and fluid; in which, generally, but not 

 always, one or many fat- globules are contained. They coagulate in 

 water and dilute acids, and are readily dissolved by alkalies. Some- 

 times the fat-globules are so numerous as to render the nucleus in- 

 visible. But a single nucleus is contained in each cell. 



2. The intercellular (or interstitial) homogeneous substance is some- 

 times hyaline, but generally finely granulated. It is permeated by 

 a peculiar fluid which has not yet been investigated. (Lehmann.) 

 Fat-globules are also often found in it. 



Finally, the permanent cartilages are invested by a fibrous mem- 

 brane, the perichondrium (e. g. costal cartilage). This is less vascu- 

 lar than the analogous sheath of the bones the periosteum, (p. 

 279, 4.) 



Chemical Composition of true Cartilage. 



The chemical characters of cartilage are, in some respects, very 

 little known. It is certain, however, that the cells and the inter- 

 cellular substance are different. The latter is converted, partially 

 at least, 2 by boiling into chondrine, in case of the true cartilages, 

 and is itself cartilageine, as has already been seen (p. 99). In reti- 

 culated cartilage chondrine exists in small amount (Roppe}, and pro- 

 bably also elasticine (p. 100). 



1 Kolliker and others term these cavities the cartilage-cells, and the true cells 

 just described, the secondary cells or nuclei. We adopt Robin's view as the correct 

 one. 



2 Lehmann infers from its behavior towards concentrated sulphuric acid that the 

 intercellular substance contains three different, though allied substances. 



