n6 



ELEMENTARY ZOOLOGY. 



127. Supportive or Connective Tissues. These are among the most 

 abundant tissues in the body and are correspondingly varied. They 

 agree among themselves only in the facts that they originate from 

 the mesoderm, are passive tissues, and tend to produce an abundance 

 of intercellular substance. 



After the cells once produce their intercellular substance, they 

 themselves play a relatively unimportant role. It is the character 

 of the intercellular substance that gives quality to the tissue. This 

 substance may vary in consistency from fluid (as in blood) to the 

 hardest organic substance known (as the enamel of the teeth) ; in 



FIG. 22. Gelatinous connective tissue bounded by epithelium, c, stellate con- 

 nectire-tissue cells; e, epithelium; /, intercellular fibres; s, gelatinous intercellular 

 substance. 



Questions on the Figure. What seems to be the relation of the 

 epithelial layer in this case to the tissue below it? What classes of 

 cells are found in the gelatinous tissue? What is their origin? 

 What is the origin and the nature of the intercellular substance? 

 Are the fibres cellular or intercellular? 



amount from almost nothing in its early embryonic form, to every- 

 thing (as in dentine and enamel) ; in arrangement and structure, 

 from a homogeneous matrix for the cells (as in some cartilages, 

 Fig. 23, A) to pure fibres (as in ordinary connective tissue), or there 

 may be a mixture of fibres and homogeneous substance, as in some 

 cartilages (Fig. 23, B) and tendons. The intercellular substance 

 may be wholly organic or very largely of inorganic salts, as in bone 

 (Fig. 24). 



The principal tissues that come under this head are gelatinous 

 connective tissue (as in the mesoderm of the jelly-fish, Fig. 22); 



