THE SUPPORTING TISSUES 



43 



as the permanent, the others as the temporary cartilages. In old age 

 many so-called permanent cartilages become calcified that is, 

 hardened and made unyielding by deposits of lime-salts in them 

 without assuming the histological character of bone, and this 

 calcification of the permanent cartilages is one chief cause of the 

 want of pliability and suppleness of the frame in advanced life. 



Hyaline Cartilage. In its purest form cartilage is flexible and 

 elastic, of a pale bluish-white color when alive and seen in large 

 masses, and cuts readily with a knife. In thin pieces it is quite 

 transparent. Everywhere except in the joints it is invested by a 

 tough adherent membrane, the perichondrium. 



When a thin slice of hyaline cartilage is examined with a micro- 

 scope it is found (Fig. 14) to consist of granular nucleated cells, 

 often collected into groups of two, four, or more, scattered through 

 a homogeneous or faintly granular ground-substance or matrix. 

 This matrix is composed of al- 

 buminoid substances, and owes 

 its origin to the cells imbedded 

 within it. At the time the 

 cartilage was in process of for- 

 mation these cells laid down 

 the matrix substance in con- 

 centric layers about them- 

 selves; thus they cut them- 

 selves off from each other and 



from Communication with the . J IG - 14. A thin slice of cartilage, mag- 



mi. L 1. nined, to show the cells embedded in the 



Outside. I he Substance Of the* homogeneous matrix, a, a cell in which 



. , rr- 4.1 , the nucleus has divided; b, a cell in which 



matrix IS Sufficiently perme- division is just complete; c,*, a group of 



able, however, for a certain f ur ce - ll8 r r^ It iu g from f ,V rt u er d , ivisio " 



of a pair like b; the new cells have formed 



interchange of food materials some matrix between them, separating 

 ., . them from another; d, d, cavities in the 



between the cartilage cells and matrix from which cells have dropped out 

 the blood, SO that the Cells during the preparation of the specimen. 



are able to remain alive, although their life is naturally an inac- 

 tive one. 



All temporary cartilages are of the hyaline type as are also the 

 costal and articular permanent cartilages and the cartilage of the 

 nose and of the windpipe. 



Elastic Cartilage is a tissue whose cartilaginous matrix is inter- 

 woven with fibers of elastic connective tissue. The result of this 



