CELLULAR DIFFERENTIATION. 



47 



is based on differences in the intercellular substance. This 

 may be fluid (as in blood) or solid (as in bone) ; it may be 

 homogeneous (as in some forms of cartilage), or fibrous; it 



FIG. 20. 



FIG. 20. Cellular Connective Tissue, showing large vacuoles, v, in the protoplasm. 



Questions on the figure. Would you say that these cells are of a 

 high or a low order of differentiation? Why? Is there any intercellular 

 substance? Where is tissue of this kind found? (See reference texts.) 



FIG. 21. 



FIG. 21. Gelatinous connective tissue, showing stellate cells (c), epithelium (e), 

 the gelatinous intercellular substance (s), and the intercellular fibres (f). 



Questions on the figure. What seems to be the relation of the epi- 

 thelial layer to the tissue below it? What classes of cells are found in 

 the gelatinous tissue? What is their origin? What is the nature of the 

 intercellular substance? Are the fibres cellular or intercellular? 



may be almost wholly organic, or very largely inorganic. The 

 principal classes are cellular connective tissues, gelatinous con- 

 nective tissue, fibrous connective tissue, cartilaginous tissue, 

 and osseous tissue. 



