GENERAL HISTOLOGY. 



85 



their physical characteristics, are called elastic fibres, and consist 

 of a substance (elastin) exceedingly resistant to all reagents. 

 Finally, in the matrix there may develop the finer connective- 

 tissue fibrils, the characteristic element of the next group; they 

 may become so prominent by increase in number as to determine 

 the character of the tissue. 



Fibrous Connective Tissue is characterized by the rich supply 

 of connective-tissue fibrillae; these are fibres of extraordinary fine- 

 ness, lying in a homogeneous basal substance, which is the less 

 evident the richer it is in fibres. The fibres may be either con- 

 fusedly arranged, crossing in all directions, or may run essentially 

 parallel and in a definite direction. Between them are found the 

 rounded, spindle-shaped or branched connective-tissue corpuscles 

 (fig. 40). It is characteristic of vertebrates that the fibres are 

 grouped into bundles. Each bundle is generally surrounded by 

 connective-tissue corpuscles, metamorphosed into flat cells. The 



FIG. 40. Fibrous connective tissue of an 

 Actinian. 



FIG. 41. Areolar fibrous connective 

 tissue. (After Gegenbaur.) 



bundles, loosely interwoven, run in all direction (areolar connec- 

 tive tissue, < cellular tissue' of the earlier authors) (fig. 41), or 

 they may be almost parallel, forming a compact mass of fibres 

 (tendinous tissue) (fig. 42). Since the fibrils of the fibrous con- 

 nective tissue of the vertebrates have another peculiarity not met 

 with elsewhere, in that they are composed of glutin, and upon 

 boiling become gelatine or glue, it is well to reserve for these 

 forms of tissue the special name connective tissue. 



Elastic Tissue. In all fibrous connective tissue there may 

 appear, as a further constituent, elastic fibres; they may indeed 



