OP THE CARTILAGES IN GENERAL. 347 



general former state with force and celerity whenever the cause 

 of flexion ceases to act. The articular cartilages alone are elas- 

 tic in the same manner as the fibre-cartilaginous tissue. 



547. The vital properties and phenomena of formation, 

 irritation and sensation, are extremely obscure in the cartila- 

 ginous tissue. It is not known if the pain felt in the articula- 

 tion, and caused by foreign bodies when between the two sur- 

 faces, is to be ascribed to the articular cartilages, or rather to 

 the synovial membrane which invests them. 



548. The functions of the cartilages depend solely upon 

 Iheir physical properties; upon their firmness, which enables 

 them to preserve the shape of certain parts ; upon their flexi- 

 bility and elasticity, which permit them to yield, at times, and 

 resume afterwards their former state. 



549. The cartilages in the embryo and foetus, are at first 

 soft, mucous and transparent, like jelly or glue; the propor- 

 tion of water at this time is very great ; in the child, they are 

 yet slightly coloured, very transparent, very soft, and slightly 

 elastic. They afterwards become white, acquire firmness, and 

 the semi-opacity which characterizes them. Later, in old age, 

 they become whiter or yellower, more opaque, less flexible, 

 less elastic, more brittle and drier; the proportion of water di- 

 minishes, and that of the earthy substance increases. They 

 at last ossify, at least in some points. This alteration com- 

 mences sometimes as soon as the adult age, but especially in 

 old age. Inflammation prematurely determinates this change. 



550. The organic action of nutrition seems to be very slow 

 in it. The use of madder does not colour them ; that. substance 

 appears to have affinity only with the earthy substance of 

 bones. They become yellow in jaundice. The cartilaginous 

 bones of the vertebral column of the lamprey appear and dis- 

 appear every year, from which they must be inferred to pos- 

 sess a great organic activity, which is also the case with the 

 rapid growth of the larynx towards the period of puberty. 



551. Accidental cartilaginous productions are very com- 

 mon, they have all the characters of natural cartilages: colour, 

 apparent homogeneity, c. They present all the varieties of 

 texture of the cartilages, and even more; we must therefore 



