TISSUES OF THE BODY. 



175 



may again undergo solution at certain points, and show a new formation 



of bone in the spaces which have 



thus been formed. But they may 



also (and this is most frequently 



the case) remain in this same 



condition to the end of life. 



It is not alone in hyaline and 

 streaky cartilage that calcifica- 

 tion is met with; it appears also, 

 though less frequently, in the 

 reticulated species. 



Softening, the last of these 

 transformative processes, may 

 affect either calcified or the soft 

 and still unchanged tissue. 



In the latter it occurs in the 

 first place very extensively in 

 the temporary cartilaginous por- 

 tions of the skeleton, during 

 fcetal life, or in early infancy, 

 but may appear likewise in older 

 permanent cartilage, though not 

 as a regular occurrence. The 

 first step of the process is a kind 

 of colloid softening of portions 

 of the matrix, taking place at iso- 

 lated points in the intercellular 

 substance, attacking the walls of 

 the capsules situated here in its 

 further progress, and forming 

 cavities into which the cartilage cells or their descendants find entrance. 

 In consequence of this process of liquefaction, a system of canals may be 

 formed, which may either open externally towards the perichondriura, or 

 enter into communication with the passages of a neighbouring portion of 

 bone containing vessels, which soon make their way into the interior of 

 the cartilage, and may be recognised there. In the mass which fills 

 up these sinuses in the cartilage, we have the before-mentioned medullary 

 cells (p. 171). 



The process of liquefaction of a portion of already calcified cartilage- 

 tissue is of a precisely similar kind. 



107. 



In inquiring now into the mode of occurrence of the several varieties 

 of cartilage, the following facts as regards the human body may be remem- 

 bered. 



Hyaline cartilaginous matter (partially fibrous, softened, or calcified, 

 however, after a certain age) forms the rudimentary skeleton in the foatus, 

 that is, the several portions of the vertebral column, of the thorax (not ex- 

 cepting the clavicle), of the shoulders, of the pelvic bones, and in addition, 

 many of those of the head. In the adult this hyaline texture remains in the 

 cartilages, clothing the ends of the bones entering into the formation of arti- 

 culations (with the single exception of the maxillary). It remains in the car- 

 tilages of the nose, and the larger ones of the larynx, namely, the thyroid 



Fig. 166. Cartilage from symphysis of a woman 

 one hundred years of age, undergoing calcification. 

 a, cartilage-cells surrounded with scattered mole- 

 cules of lime-salts ; 6, c, d, more copious deposit in 

 the intercellular substance, and around the cells ; e, 

 true bony tissue. 



