CARTILAGE. 161 



idosmose, to diffuse themselves through an aqueous liquid, provided 

 the latter be alkaline. 



264. In the simpler forms of Cartilage, we have an example of a tissue 

 of remarkable permanence, composed entirely of cells scattered through 

 an intercellular substance. This substance has received the distin- 

 guishing appellation of Chondrine, which marks it as the solidifying 

 ingredient of Cartilage (177). All the Cartilages of the foetus, those 

 which are to be converted into bone, as well as those which are to 

 remain unossified, are composed of it ; and yet, as soon as the process 

 of Ossification commences, the chondrine is replaced by Gelatine, which 

 is the sole organic constituent of the animal basis of bones. The per- 

 manent cartilages, however, still contain only Chondrine ; but if acci- 

 dental bony deposits should take place in them (as frequently happens 

 in old persons, especially in the cartilages of the ribs), the Chondrine 

 gives place to Gelatine. This change of composition is coincident, as 

 we shall hereafter see, with a complete change in texture ; the basis of 

 bony tissue not being Cartilage (as commonly imagined), but consisting 

 of a substance much more nearly allied to the white fibrous tissue. It 

 is only in the pure cellular cartilages, in which the intercellular sub- 

 stance presents no trace of organization, that Chondrine occurs. Those 

 of the j^ro-cartilages ( 269), in which the intercellular substance has 

 the characters of the White fibrous tissue, yield gelatine on boiling, in 

 the manner of the ligaments and tendons ; whilst those which contain 

 much of the Yellow or, elastic tissue, undergo very little change by boil- 

 ing, and only yield, after several days, a small quantity of an extract 

 which does not form a jelly, but which has the other chemical properties 

 of Chondrine. 



265. Besides the organic compounds already described, most Carti- 

 lages contain a certain amount of mineral matter, which forms an ash 

 when they are calcined. This ash contains a large proportion of car- 

 bonate and sulphate of soda, together with carbonate of lime, and a 

 small quantity of phosphate of lime ; as age advances, the proportion 

 of the soluble compounds diminishes, and the phosphate of lime predo- 

 minates. This is especially the case in the costal cartilages, which 

 almost invariably become converted into a semi-ossified, substance, in 

 old persons ; and it is remarkable that, even before they have themselves 

 become thus condensed, they are united by ossific matter, when they 

 have undergone fracture. 



Fig. 38. 



Cartilage of Mouse's ear. 



. When a pure Cellular Cartilage is examined microscopically. 



