330 THE SOLIDS. 



cellular tissue ; it constitutes the principal portion of the 

 ligamenta subflava and nuchre, of the transverse fascia of 

 the abdomen, of the cricothyroid and thyrohyoid membranes, 

 of the chordae vocales, of the internal lateral ligament of the 

 lower jaw, of the stylo-hyoid ligaments, of the middle coat of 

 the arteries, and of the membrane uniting the rings of the 

 trachea and its ramifications. It is also met with in con- 

 siderable quantities beneath the mucous membrane of the 

 esophagus, at the base of the epiglottis, in maintaining which 

 in the erect position it is probably mainly instrumental, in the 

 lungs and in the integuments of the penis. 



The elastic cellular tissue presents some differences of ap- 

 pearance and structure, in certain of the situations in which it 

 is encountered : thus, in the tendons and in the smaller blood- 

 vessels (Plate XL.J&7S. 1, 2, 3. 5.) the fibres are very slender, 

 appear to be but little branched, and contain at intervals 

 nuclei in the same manner as do the fibres of unstriped 

 muscles ; in the reticular cellular tissue again, they are slen- 

 der, unbranched, and without nuclei (see Plate XXXIX. 

 Jig. 7.) ; in the ligamenta flava and nuchae, in the cricothyroid 

 and thyrohyoid membranes, the fibres are thick, much 

 branched, curled, and interwoven, but they do not present 

 nuclei (see Plate XL. fig. 1.) ; in the larger arteries, the 

 fibres are slender, and are united together so as to form 

 areolae (see Plate XL. fig. 2.), while in the smaller blood- 

 vessels they are distinctly nucleated, as already observed. 



There is little doubt but that the several forms of elastic 

 tissue just described do really represent different stages and 

 states of the same structure ; and it will be observed, that 

 some of them, and especially that of the small blood-vessels, 

 approach very closely in structure and appearance to that 

 of unstriped muscular fibre : the fibres of the former differ, 

 however, in being sparingly branched, and in their more 

 slender diameter. 



It is not easy, without the addition of re-agents, to distin- 

 guish the two forms of fibrous or cellular tissue from each 

 other when mixed together: nevertheless, when the two are 

 well separated, the elastic fibres may be frequently singled 

 out from the inelastic, in consequence of their presenting 



