34 



AN INTRODUCTION TO ZOOLOGY 



described as hyaline cartilage. The supra-scapular yields another 

 variety of cartilage, namely, calcified cartilage, so called because the 

 matrix is more or less impregnated with calcareous granules. These 

 may be removed by immersion for some time in weak hydrochloric 

 acid, and the matrix then appears full of a number of tiny spaces in 

 which the granules were previously lodged. 



Young cartilage is easily distinguishable from old, because it 

 possesses much less intercellular matrix, and consequently a 

 relatively larger number of cells. All cartilage on boiling yields a 

 substance called chondrin, which sets in a jelly when cold. It is 



* : - ' 



V ** 



ft V > 



FIG 8. Section of cartilage, showing cartilage cells (c.c.) embedded in the 

 transparent intercellular matrix or ground substance (m). x 390. 

 From a photograph (Dendy). 



covered by a tissue containing a rich supply of blood-vessels, known 

 as the perichondrium. 



Bone differs markedly from cartilage in many ways, 

 although it agrees with it in being built up of cells surrounded by a 

 large amount of intercellular matrix.. The matrix consists of a 

 tough organic basis, that yields gelatin on boiling, densely impreg- 

 nated with inorganic salts. The intimate way in which organic 

 and inorganic constituents are mixed may be seen by taking two 

 bones and placing one in weak Hydrochloric acid and heating the 

 other in a test tube until it is thoroughly charred. The former will 

 have all the inorganic salts removed, i.e. be decalcified, and will be 

 soft and flexible, whereas the latter will have no organic matter left, 

 and will be hard and very brittle. Both, however, will remain 



