MOVEMENTS DUE TO ELASTICITY. 443 



of the inelastic fibres, it is frequently called the yellow elas- 

 tic tissue. 



The first variety of elastic tissue is composed of small 

 fibres, generally intermingled with fibres of the ordinaiy 

 inelastic tissue. These are sometimes called by the French, 

 dartoic fibres. They possess all the chemical and physical 

 characters of the larger fibres, but are excessively minute, 

 measuring from 25 i 00 to ^^ or -^^ of an inch in diame- 

 ter. 1 If we add acetic acid to a preparation of ordinary 

 connective tissue, the inelastic fibres are rendered semitrans- 

 parent, but the elastic fibres are unaffected and become very 

 distinct. They are then seen isolated that is, never arranged 

 in bundles always with a dark, double contour, branching, 

 brittle, and when broken, their extremities curled and pre- 

 senting a sharp fracture, like a piece of India-rubber. These 

 fibres pursue a wavy course through the bundles of inelastic 

 fibres in the areolar tissue and in most of the ordinary fibrous 

 membranes, and here they exist as an accessory anatomical 

 element. They are found in greater or less abundance in the 

 situations just mentioned ; also in the ligaments (but not the 

 tendons) ; in the layers of involuntary muscular tissue ; the 

 true skin ; the true vocal cords ; 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 situa- 

 tions 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 out- 

 lines, anastomosing, undulating or curved in the form of the 

 letter S, presenting the same curled ends and sharp fracture 

 as the smaller fibres. These measure from g^ to ^Vfr of 

 an inch in diameter. 2 Their type is found in the ligamenta 

 subflava and the ligamentum nuchse. They are also found 



1 POUCHET, Freds cCJustologie humaine, Paris, 1864, p. 62. In order to 

 secure as much uniformity as possible in our measurements of microscopic 

 structures, we have generally followed the French school of histologists. 



2 POUCHET, loc. cit. 



