CARTILAGE. 



101 



joints it is invested by a tough adherent membrane, the 

 perfchondrium, which resembles in structure and function 

 the periosteum of the bones. When boiled for a long time 

 in water such cartilages yield a solution of chondn'n, which 

 differs from gelatin in minor points but agrees with it in 

 the fact that its hot watery solutions " set" or gelatinize on 

 cooling. When a thin slice of hyaline cartilage is examined 

 with a microscope it is found (Fig. 42) to consist of gran- 

 ular nucleated cells, often collected into groups of two, 

 four, or more, scattered through a homogeneous or faintly 

 granular ground substance or matrix. Essentially, cartilage 

 resembles bone, being made up of protoplasmic cells and a 

 proportionately large amount of non-protoplasmic mtereel- 



FIG. 42. -Hyaline cartilage, c, a cell with several nuclei, and about to divide 

 *, a cell which has divided into two; a, a group of four cells such as would re- 

 sult from a repetition of the division of b The granules of the matrix are 

 represented much too coarse and conspicuous. 



lular substance, the cells being the more actively living 

 part and the matrix their product. Examples of this hya- 

 line variety (so called from its glassy transparent appear- 

 ance) are found in all the temporary cartilages, and in the 

 costal and articular among the permanent. 



They rarely contain blood-vessels except at those points 

 where a temporary cartilage is being removed and replaced 

 by bone; then blood-vessels run in from the perichondrium 

 and form loops in the matrix, around which it is absorbed 

 and bony tissue deposited. In consequence of the usual 

 absence of blood-vessels the nutritive processes and ex- 

 changes of material must be small and slow in cartilage, as 



OF THE 



UNIVERSITY 



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