MOVEMENTS DUE TO ELASTICITY. 



463 



appearance of the inelastic fibres, it is frequently called the yellow, elastic 

 tissue. 



The first variety of elastic tissue is composed of small fibres, generally in- 

 termingled with fibres of the ordinary inelastic tissue. They possess all the 

 chemical and physical charac- 

 ters of the larger fibres, but are 

 very fine, measuring T^^HF to 

 iroVo" or s 0*0 tf ^ an inch (1 to 4 

 or 5 /u,) in diameter. If acetic 

 acid be added to a preparation 

 of ordinary connective tissue, 

 the inelastic fibres are rendered 

 semi-transparent, but the elas- 

 tic fibres are unaffected and be- 

 come quite distinct. They are 

 then seen isolated, that is, never 

 arranged in bundles, generally 

 with a dark, double contour, 

 branching, brittle, and when 

 broken, their extremities curled 

 and presenting a sharp fract- 

 ure, like a piece of India-rubber. These fibres pursue a wavy course between 

 the bundles of inelastic fibres in the areolar tissue and in most of the ordinary 

 fibrous membranes. They are found in greater or less abundance in the 

 situations just mentioned ; in the ligaments, but not the tendons ; in the lay- 

 ers of non -striated muscular tissue ; the true skin ; the true vocal chords; the 

 trachea, bronchial tubes, and largely in the parenchyma of the lungs ; the 

 external layer of the large arteries ; and, in brief, in nearly all situations in 

 which the ordinary connective tissue exists. 



The second variety of elastic tissue is composed of fibres, larger than the 

 first, ribbon-shaped, with well-defined outlines, anatomosing, undulating or 

 curved in the form of the letter S, presenting the same 

 curled ends and sharp fracture as the smaller fibres. 

 These measure j-^ to 3-5^5- of an inch (5 to 8 /A) in di- 

 ameter. Their type is found in the ligamenta subflava 

 and the ligamentum nuchse. They are also found in 

 some of the ligaments of the larynx, the stylo-hyoid liga- 

 ment and the suspensory ligament of the penis. 



The third variety of elastic tissue is found forming 

 FIG.' 148. Large elastic the middle coat of the large arteries, and it has already 

 ^Kmbran)"from\ e he been described in connection with the vascular system. 

 Carotid of \heLri e ; The fibres are lar g e and flat > inosculating freely with 

 fe?s SSmkCT) diame ~ each other by short, communicating branches. These 

 anastomosing fibres, forming the so-called fenestrated 

 membranes, are arranged in layers, and the structure is sometimes called the 

 lamellar elastic tissue. 



