CARTILAGE. 813 



CHAPTBK VI. 



CARTILAGE. 



CARTILAGE is sometimes a simple, but generally a compound tis- 

 sue. It is described here more especially because of the advantage 

 of a knowledge of the structure of cartilage as preliminary to that 

 of the development of bone. 



Cartilage is a solid, elastic, bluish, milk-white, or yellowish sub- 

 stance, presenting two varieties : 



1. Simple cellular cartilage. 



2. Compound cartilage ; consisting of cells and a homogene- 



ous intercellular substance. 



1. Very few instances of the simple cellular cartilage, or cartilage 

 without interstitial substance, occur in the adult mammal. To this 

 class, however, belong the chorda dorsalis of the human embryo, 

 and of many adult fishes. Many, indeed, of the foetal cartilages 

 are merely cellular; as are also the gill laminas of fishes in part, 

 and those of the external ear of many mammalia. Fig. 200 shows 

 the cells of the chorda dorsalis of the lamprey, and Fig. 201, the 

 cellular cartilage of the mouse's ear. 



Fig. 200. Fig. 201. 



-2. 



Fig. 200. Four nucleated cells from the chorda dorsalis of the lamprey. 1. Nucleus with nucleo- 

 lus. 2. Another, seen in profile. 

 Fig. 201. Cellular cartilage of mouse's ear. 



2. The compound cartilages (those with intercellular substance), 

 are of two kinds : 1. True cartilage (or hyaline cartilage), the inter- 

 cellular substance being homogeneous, and yielding chondrine on 



