320 



THE TISSUES. 



surrounding parts. 



Fig. 210. 



Enchondroma : 



microscopic structure. 

 Lebert) 



(After 



It, however, sometimes ulcerates and pours 

 out an exhausting discharge. 

 When externally situated, it is lo- 

 bulated and surrounded by an ex- 

 pansion of the periosteum. When 

 internal, it presents a semi-elastic 

 feel, and, on section, the knife 

 passes through a thin crackling 

 shell of bone, and then shows a 

 white cartilaginous mass; which 

 on microscopic examination, some- 

 times cannot be distinguished from 

 true cartilage, and at others resem- 

 bles fibre-cartilage. Figs. 207, 208, 

 and 209 show the structure of the 

 first variety; and Fig. 210, that 

 which resembles fibro-cartilage. 

 The former yields chondrine on boil- 

 ing, and the latter glutin. The 

 external variety has no investment 

 of bone, and is met with chiefly in the pelvis, cranium, and ribs. 



Enchondroma generally, but not always, manifests no disposition 

 to ossification. It is chiefly met with in early life, and Miiller has 

 shown that it is generally due to mechanical injury interfering with 

 the development of bone at the period when ossification occurs and 

 bone is formed ; and the process usually commences at the point of 

 attachment of the growth to the bone on which it is developed. 

 When completely ossified, the enchondroma becomes an exostosis. 



4. Atrophy of cartilage is not uncommon. Here the hyaline in- 

 tercellular substance, especially in case of the articular cartilages, is 

 replaced by a soft ligamentous or fibrous structure, easily scraped 

 by the knife, and of a dirty brownish-yellow color, the fibres disap- 

 pearing under the action of acetic acid. The cartilage-cells become, 

 at the same time, more or less filled with fat-globules. The inter- 

 vertebral cartilages of aged persons are usually of a dusky color, 

 and dry ; the intercellular substance being also fibrous, and contain- 

 ing pigment-cells. Atrophy of the articular cartilages may be pro- 

 duced by cancer or sarcoma, when occurring near them in the ex- 

 tremities of the bones. 



5. Necrosis (or death) of cartilage occurs as in the cartilage of 

 the larynx from inflammation of the perichondrium (perichondri- 

 tis Albers). A formation of pus in the cancelli of the articular 

 extremities of bone, often produces necrosis of the articular car- 

 tilages. 



6. Cartilage is liable to fatty degeneration, this affecting both the 

 cells and the intercellular substance ; both losing their transparency, 

 and ultimately becoming wholly unrecognizable. Suppuration in 

 the contiguous bone sometimes produces this effect. 



