82 



GENERAL ANATOMY OF THE TI8SUES. 



times expanded in a membranous form, and sometimes penetrates other 

 tissues to various depths. A modification of this fibrous elastic network 

 is formed by the elastic membranes, in which the fibres are so closely 

 interwoven, that a connected membrane arises, which in the most extreme 

 cases no longer exhibits any indication of its previous nature, and ap- 

 pears as a perfectly homogeneous membrane with smaller gaps (the 

 fenestrated membrane of Henle). 



Fig. 23. Fig. 24. 



Fig. 25 



t 



,1 !■ 



■\ 



Hi 





/i:^ 



Chemically, elastic tissue presents very decided reactions, but the 

 composition of its substance is not yet exactly known. In cold concen- 

 trated acetic acid, the elastic fibres, except that they swell a little, are 

 not afiected ;* if boiled for a whole day, however, they are gradually dis- 



FiG. 23. — Two secondary bundles of connective tissue from the arachnoid of man with 

 coiled and straight (intestinal) fine elastic fibres, and acetic acid added ; magnified 350 

 diameters. 



Fig. 24. — Network of fine elastic fibre from the peritoneum of a child; magnified 350 

 diameters. 



Fig. 25. — Elastic membrane from the tunica media of the carotid of the horse; magni- 

 fied 350 diameters. 



* [The difficulty with which acetic acid acts on elastic (yellow fibrous) tissue, presents an 

 important means of distinction between it and the connective (white fibrous) tissue, the 

 fibres of which are readily rendered transparent by its action. In tissues in which the 

 elastic fibres are mixed up, or concealed by the fibres of connective tissue, acetic acid 



