THE CONNECTIVE TISSUES. 



IO9 



substance and which refracts the light more strongly. This zone is 

 generally known as the capsule of the cartilage cells. As pre- 

 viously stated, the matrix or ground-substance, develops in the 

 exoplasm of the protoplasmic syncytium from which cartilage has 

 its origin, while the endoplasm and nuclei form the cartilage cells. 

 Cartilage cells, as such, are of various shapes, and have no typical 

 appearance. They are usually scattered irregularly throughout the 

 matrix, but are often arranged in groups of two, three, four, or even 

 more cells. At the periphery of cartilage, either where it borders 

 upon a cavity (articular cavity) or where it joins the perichondrium, 

 the cells are arranged in several rows parallel to the surface of the 

 tissue. Cartilage cells often contain glycogen, either in the form 

 of drops or diffused throughout their protoplasm. 



Cartilage grows by intussusception, and an appositional growth, 

 although in a lesser degree, also takes place. It occurs where the 

 cartilage borders upon its connective -tissue sheath or perichondrium, 



\ 



'tito, 



Fig- 77- From a section through the cranial cartilage of a squid (after M. Fiirbringer, 



from Bergh). 



a vascular, fibrous-tissue membrane composed of white and elastic 

 fibers, which covers the cartilage except where it forms a joint sur- 

 face. The relations of the cartilage and perichondrium are extremely 

 intimate. Fibers are seen passing from the perichondrium into the 

 cartilaginous matrix, and the connective-tissue cells appear to change 

 directly into cartilage-cells. 



Certain observers (Wolters, Spronk, and others) have described a 

 system ofcanaliculi in the ground substance, which are said to unite 

 the lacunae and are thought to serve as channels for the passage oT 

 lymph. Such structures are, however, not generally recognized. It 

 is an interesting fact, however, that the cartilage of certain inverte- 

 brate animals, the cephalopoda, shows cells with anastomosing pro- 

 cesses. (Fig. 77.) In this case the cartilage-cell is similar to a 

 bone-cell, thus theoretically allowing of the possibility of the meta- 

 morphosis of the elements of cartilage into those of bone (M. Fiir- 

 bringer). 



