FIBROUS TISSUE. 



75 



such fineness that they possess no appreciable width. The fibrils are united by and 

 embedded within a semifluid ground-substance , which may be present in such meagre 

 amount that it suffices only to hold together the fibrillse, or, on the other hand, it 

 may constitute a large part of the entire intercellular tissue, as in the matrix of hya- 



FiG. 97. 



'fn.^ 



Fig. 98. 





Pigmented connective-tissue cells from choroid. 

 X 400- 





"f is^fe 







.x 



Surface view of portion of omentum. X 130. Fi- 

 brous and elastic tissue are arranged as a fenestrated 

 membrane; the nuclei belong to the connective-tissue 

 and the endothelial cells. 



Fig. 99. 



V^-J^-a?" 



line cartilage. Depending upon the dis- 

 position of the bundles, fibrous tissue 

 occurs in two principal varieties, — areolar 

 and dense connective tissue. 



The fibrous tissue of the areolar 

 group is arranged in delicate wavy bun- 

 dles which are loosely and irregularly in- 

 terwoven, as seen in the subcutaneous 

 layer, the intervening clefts being largely 

 occupied by the ground-substance. In 

 the denser connective tissues the fibrous 

 tissue is disposed with greater regularity, 

 either as closely packed, parallel bundles, 

 as in tendon and aponeuroses, or as intimately felted, less regularly arranged, bands 

 forming extended sheets, as in fasciae, the cornea, and the dura mater. The ground- 

 substance uniting the fibrillae of dense connective tissues often contains a system of 



definite interfascicular lymph-spaces^ 

 which, in suitably stained prepara- 

 tions, appear as irregularly stellate 

 clefts that form, by union of their 

 ramifications, a continuous net-work 

 of channels for the conveyance of the 

 tissue-juices throughout the dense 

 connective substances ; in non-vascu- 

 lar structures, as the cornea and the 

 denser parts of bone, these systems 

 of intercommunicating lymph-spaces 

 serve to convey the nutritive sub- 

 stances to the connective-tissue cells 

 which lie within these clefts. Fibrous 

 tissue yields gelatin on boiling in 

 water, and is not digested by pan- 

 creatin ; on the addition of acetic acid 

 this tissue becomes swollen and trans- 

 parent, the individual fibrillae being 

 no longer visible. 



Reticular Tissue. — The in- 

 vestigations of Mall have emphasized 

 the presence of a modified form of fibrous tissue in many localities, especially in 

 organs rich in lymphoid cells. This variety of intercellular substance, known as 

 reticular tissue or reticulum, consists of very fine fibrillae, either isolated or associated 



■S,~<KV^ 



^'>. 



C 



'>,-...V 





t 



\ 

 f 



^, 





£^^' 





■^1 



ir*s 







^;.^^ 



Cell-spaces of dense connective tissue from cornea of calf; 

 the surrounding ground-substance has been stained with argen- 

 tic nitrate. X 525. 



