CARTILAGE. 



43 



Fig. 14. 



may rather be looked upon as involutions of the perichondrium. The ensiform 

 cartilage may be regarded as one of the costal cartilages, and the cartilage of 

 the nose and of the larynx and trachea 

 resemble them in microscopical charac- 

 ters, except the epiglottis and cornicula 

 laryngis, which are of the reticular 

 variety. 



The hyaline cartilages, especially in 

 adult and advanced life, are prone to 

 calcify that is to say, to have their 

 matrix permeated by the salts of lime, 

 without any appearance of true bone. 

 This process of calcification occurs also, 

 and still more frequently according to 

 Eollett, in such cartilages as those of the 

 trachea, which are prone afterwards to 

 conversion into true bone. It is on the 

 confines of true ossification that this cal- 

 cerous change or degeneration is most 

 liable to occur, so that it is rare to find 

 true bone and true cartilage in juxtapo- 

 sition at the confines of the normal ossi- 

 fication, as for instance at the joint ends, 

 at the ends of the ribs, in the symphysis 

 pubis and intervertebral cartilages. 



Fibro-cartilage consists of a mixture of white fibrous and cartilaginous tissues 

 in various proportions ; it is to the first of these two constituents that its flexi- 



Costal cartilage from a man seventy-six years 

 of age, showing the development of fibrous struc. 

 ture in the matrix. In several portions of the 

 specimen, two or three generations of cells are seen 

 inclosed in a parent cell-wall. (High power.) 



White fibrous cartilages from the semilunar disk of the patella joint of an ox, (Magnified 100 times.) 



bility and toughness is chiefly owing, and to the latter its elasticity. The 

 fibro-cartilages admit of arrangement into four groups interarticular, connect- 

 ing, circumferential, and stratiform. 



The interarticular fibro-cartilages (menisci) are flattened fibro-cartilaginous 

 plates, of a round, oval, or sickle-like form, interposed between the articular 

 cartilages of certain joints. They are free on both surfaces, thinner toward 

 their centre than at their circumference, and held in position by their extremi- 

 ties being connected to the surrounding ligaments. The synovial membrane 

 of the joint is prolonged over them a short distance from their attached margin. 

 They are found in the temporo-maxillary, sterno-clavicular, acromio-clavicular, 

 wrist and knee-joints. These cartilages are usually found in those joints most 

 exposed to violent concussions, and subject to frequent movement. Their use 



