THE CONNECTIVE TISSUES. 



1089 



have developed to the practical exclusion of the other elements. It is found in 

 the ligamenta subflava, in the vocal cords, in the longitudinal coat of the trachea 

 and bronchi, in the inner coats of the blood-vessels, especially the larger arteries, 

 and to a very considerable extent in the thyro-hyoid, crico-thyroid, and stylo-hyoid 

 ligaments. It is also found in the ligamentum nuchae of the lower animals (Fig. 

 614). In some parts, where the fibres are broad and large and the network close, 

 the tissue presents the appearance of a membrane, with gaps or perforations cor- 

 responding to the intervening space. This is to be found in the inner coat of the 

 arteries, and to it the name of fenestrated membrane has been given by Henle. 

 The yellow elastic fibres remain unaltered by acetic acid. Chemically they are 

 composed of the albuminoid body, elastin. 



Vessels and Nerves of Connective Tissue. The blood-vessels of connective tissue 

 are very few that is to say, there are few actually destined for the tissue itself, 



FIG. 614. Yellow elastic tissue. High power. 



although many vessels may permeate one of its forms, the areolar tissue, carrying 

 blood to other structures. In white fibrous tissue the blood-vessels usually run 

 parallel to the longitudinal bundles and between them, sending transverse com- 

 municating branches across, and in some forms, as the periosteum and dura mater, 

 they are fairly numerous. , In the yellow elastic tissue the blood-vessels also run 

 between the fibres, and do not penetrate them. Lymphatic vessels are very numer- 

 ous in most forms of connective tissue, especially in the areolar tissue beneath the 

 skin and the mucous and the serous surfaces. They are also found in abundance 

 in the sheaths of tendons, as well as in the tendons themselves. Nerves are 

 to be found in the white fibrous tissue, where they terminate in a special manner; 

 but it is doubtful whether any nerves terminate in areolar tissue ; at all events, 

 they have not yet been demonstrated, and the tissue is possessed of very little 

 sensibility. 

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