52 



FIFTH LECTURE 



appearance in separated portions of the tissue. The inter- 

 weaving of the fibres varies considerably. When loosely in- 

 terwoven, the bundles running in one plane are united by 

 homogeneous, membranous intermediate substance. 



Acetic acid, an important reagent, causes the bundles to 

 swell up rapidly and the fibrous appearance to disappear. By 

 washing out, or neutralizing that reagent, the former ap- 

 pearance is restored. 



Previously, the excess of connective-tissue fibrilla very fre- 

 quently concealed the intermingled elastic elements. Now, 

 in the acid preparation, the latter make their appearance 



Fig. 52. — Human elastic fibres. 



(Fig. 52). We perceive, firstly, the finest, frequently corru- 

 gated fibrillae without ramifications (a). They remind one of 

 the connective-tissue fibrillae ; but the darker appearance, 

 and the power of resisting acetic acid, permit of no mis- 

 take. Other elastic fibres are larger. 



Very frequently there are ramifications, and by the com- 

 munication of the branches an elastic net-work is formed. 

 We perceive such an one at b, with large meshes, and fibres 

 which measure only 0.0014 to 0.0025 mm. in thickness. 



