ELASTIC TISSUE. 



Ixxvii 



1. Forming the ligamenta subftava, which extend between the arches of adjacent 

 vertebrae ; these ligaments, while they permit the bones to be drawn apart in flexion 

 of the body, aid in restoring and maintaining their habitual approximation in the 

 erect posture so far, therefore, relieving the constant effort of the erector muscles. 



2. Constituting the chief part of the stylohyoid, thyrohyoid, and cricothyroid liga- 

 ments, and those named the vocal cords. Also extending, in form of longitudinal 

 bands, underneath the mucous membrane of the windpipe and its ramifications. 



3. Entering, along with other textures, into the formation of the coats of the blood- 

 vessels, especially the arteries, and conferring elasticity on these tube?". 4. Beneath 

 the mucous membrane of the gullet and lower part of the rectum, also in the tissue 

 which surrounds the muscular coat of the gullet externally. 5. In the tissue which 

 lies under the serous membranes in certain parts. 6. In many of the fasciae, where 

 it is mixed with much areolar tissue. 7. Largely in the suspensory ligament and 

 subcutaneous tissue of the penis. 8. In considerable quantity in the tissue of the 

 skin. 



The elastic tissue in its purest and moat typical condition, such as is seen 

 in the ligamentum nuchse of quadrupeds and the ligamenta subflava of the 

 human spine, has a yellow colour more or less decided ; it is extensible and 

 elastic in the highest degree, but is not so strong as ordinary fibrous liga- 

 ment, and it breaks across the direction of its fibres when forcibly stretched. 

 Its fibres may be easily torn separate in a longitudinal direction ; they are 

 often gathered into irregular fasciculi which run side by side but 'join at 

 short distances by slips with one another, and are further connected by 

 areolar tissue, which is always intermixed with them in greater or less 

 quantity. Elastic ligaments are also covered outwardly with a sheath of 

 areolar tissue. 



When the elastic fibres are mixed up with a large proportion of some 

 other kind of tissue, their yellow colour may not appear, but they can 

 always be recognised by their microscopic 



characters. When viewed under a tolerably Fig. XXXVII. 



high magnifying power, they appear quite 

 transparent, with a remarkably well- 

 defined dark outline (fig. XXXVIL). They 

 run side by side, following a somewhat 

 bending course, but with bold and wide 

 curves, unlike the undulations of the white 

 connective filaments. As they proceed they 

 divide into branches, and join or anas- 

 tomose together in a reticular manner. 

 Elastic networks may be composed of fine 

 fibres with wide meshes, and this is the 

 character of all at first ; but while some 

 continue in this state, in others the elastic 

 fibres grow larger and broader and the 

 intervening spaces narrower, so that the 

 tissue may acquire a lamellar character 

 and present the appearance of a homo- 

 geneous membrane, which may be either 

 entire, or with gaps or perforations at short 

 intervals, in which case it constitutes the 

 fenestrated membrane of Henle, found in 

 the coats of the blood-vessels. A re- 

 markable character which elastic fibres exhibit in many specimens, is 

 their singular tendency to curl up at their broken ends ; and these 



Fig. XXXVII. ELASTIC FIBRES 

 FROM THE LIGAMENTA SUBFLAVA, 

 MAGNIFIED ABOUT 200 DIAMETERS. 



