SECT. 25.] 



ELASTIC TISSUE. 



5 1 



nuclear fibres ; and since, lastly, the latter are not developed from 

 nuclei alone, it is better to discard the name 

 nuclear fibres entirely, and to divide the 

 elastic fibres into finer and thicker. 



The elastic fibres occur cither isolated as 

 longer or shorter fibres, straight or spirally 

 wound round other parts (bundles of con- 

 nective tissue, nerves), and, in this case, 

 usually belong to the finer kind ; or, anasto- 

 mosing, with fibres of various thickness, and 

 then form the so-called elastic fibrous network 

 (fig. 18). This is sometimes spread out in form 

 of a membrane, and sometimes traverses 

 other tissues at different depths. The elastic 

 membranes represent a modification of this 

 clastic fibrous network, in which the fibres 

 are so denselv interwoven as to give rise to JIa s nined 3ft0 times - 

 a continuous membrane, which, in extreme cases, retains no hidi- 

 ng. 19. cation of its former nature, and appears as a per- 

 j-j. fectly homogeneous membrane with small open- 

 ||1 ings (fenestrated membrane, Henle) (fig. 19) . 



In its chemical relations, elastic tissue pre- 

 sents very definite reactions, still the compo- 

 sition of its substance is not yet accurately 

 known. In cold concentrated acetic acid, the 

 elastic fibres, except that they swell out some- 

 what, are not at all affected ; on the other hand, 

 bv some days continued boiling in the acid, 



Nitric acid renders 



Network of fine elastic fibres, 

 from the peritoneum of a child. 



> . 



M 



Elastic membrane, from 

 the tunica media of the ca- 

 rotid of the horse. Magni- they gradually dissolve. 



them yellow; Milton's re-agent for proteine 

 compounds, red ; whilst they are not reddened by sulphuric acid and 

 sugar. In moderately concentrated solution of caustic potash, 

 elastic tissue remains for a long time unaltered in the cold, except 

 that it swells up and becomes somewhat pale; on being heated 

 with that solution for days, it is transformed into a gelatinous 

 mass. This tissue does not dissolve in water, even when boiled 

 for sixty hours; but after being boiled for thirty hours at 160 

 (3 20 F.) in Papiris digester, it is converted into a brownish sub- 

 stance, smelling like gelatine, but not gelatinizing, which is pre- 

 cipitated by tannic acid, tincture of iodine, and corrosive subli- 

 mate, but not by the other tests of chondrin. 



In a 'physiological point "of view, we have, above all, to notice the 



