82 THE CONNECTIVE TISSUES, BY A. ROLLETT. 



from those of the connective tissue, not only by the resistance 

 which they offer to the above-mentioned agents, but also by 

 the circumstance that they present a remarkable tendency to 

 branch and form networks. They are sometimes only sparingly 

 present, and then usually exhibit the form of cylindrical delicate 

 fibrils of about the same size as those of the connective tissue 

 slightly branched, and forming long large meshes, as in the 

 tendons of man ; or, on the other hand, they may be present in 

 greater numbers, may branch repeatedly, and, being connected 

 by frequent anastomoses, form a fine delicate plexus, as on the 

 surface of many serous and mucous membranes. The several 

 fibres may also coalesce to form one of considerable thickness ; 

 they may also expand in the form of flattened trabeculse, which 

 combine with similar or still finer fibres proceeding from the 

 branches of the trabeculse, to form a very characteristic plexus, 

 as in the cutis and the lungs. In several places, as, for instance, 

 in the ligamentum nuchse of animals, in the ligamenta sub- 

 flava of the vertebral column, and in the elastic tissue of the 

 arteries, the elastic fibres exist in such quantity that they are 

 commonly regarded as forming an independent elastic tissue or 

 membrane. The fibres here are for the most part thick, and 

 branch and communicate at more or less acute angles, so that 

 only narrow and elongated, or small round or oval meshes, lie 

 between them. The trabeculse often appear very much ex- 

 panded, or become fused together into elastic plates or mem- 

 branes, which are perforated by sharply defined foramina consti- 

 tuting the so-called fenestrated membrane of the arterial tunics. 

 The elastic fibres undergo no change from exposure to the 

 action of either dilute or concentrated acetic acid, and they resist 

 for a very long period, at ordinary temperature, the action both 

 of potash and soda. The latter forms one of the best means of 

 bringing them into view. Concentrated sulphuric acid makes 

 the elastic fibres clearer without immediately causing them to 

 swell up, and its action requires to be continued for many days 

 before the fibres swell and begin to dissolve. The elastic 

 fibres do not dissolve on boiling, at least in the time requisite 

 to convert the collagen of connective tissue into gelatine ; and if 

 connective tissue and albuminoid substances have been removed 

 from tke specimen, as, for instance, from the ligamentum nuchse, 



