ELASTIC TISSUE. 



[ 278 ] 



ELASTIC TISSUE. 



Gewebel. d. Mensch.-, Rollett, Strieker's 

 Geweb. i. 59. 



ELASTIC TISSUE of animals, or yel- 

 low fibrous tissue, occurs in the ligamenta 

 subflava of the vertebrae, in the thyro-hyoid 

 and cricoid membranes, the vocal chords, 

 the trachea, forming the longitudinal elastic 

 bands of that tube and its branches, in the 

 internal lateral ligament of the jaw, the 

 stylo-hyoid ligament, the transversalis fas- 

 cia of the abdomen, the blood-vessels, and 

 almost everywhere mixed with the fibres 

 of connective tissue. 



It differs from white fibrous tissue in its 

 elasticity and its yellow colour. But some 

 physiologists regard it as a variety of this. 



Its elementary form is that of round or 

 flattened fibres, varying in size from an 

 almost immeasurable tenuity to that of 

 1-2200" or even more ; the finer ones have 

 been termed nuclear fibres by the Germans ; 

 thev are either isolated, arranged in bundles, 

 or branching and anastomosing (fig. 189), 

 sometimes undulating or spiral, at others 

 nearly straight. When broken, they curl 

 up, the ends appearing abrupt or truncated. 

 They are highly refractive, their edges 

 appearing dark, well-defined, and mostly 

 smooth, but sometimes toothed or serrated. 

 Sometimes they exhibit transverse .cracks 

 upon the surface. 



Fig. 188. 



Fig. 189. 



Fig. 188. Network of elastic tissue, from the middle 

 coat of the pulmonary artery of the horse. Magnilied 

 350 diameters. 



Fig. 189. Network of fine elastic fibres from the 

 peritoneum of a child. Magnified 350 diameters. 



They are easily distinguishable from fibres 

 of connective tissue by the use of acetic acid, 



which has little or no effect upon them ; and 

 this is also the case with solution of potash. 

 Sometimes by their anastomoses they form 

 fibrous networks (fig. 189), or plates perfo- 

 rated irregularly by holes fenestrated 

 membranes (fig. 188). The fibres are also 

 themselves sometimes transversely perfo- 

 rated by irregular rounded apertures. 



Chemically, elastic tissue consists of elas- 

 tine. It is coloured red by Millon's test, 

 but not by that of Pettenkofer, and does 

 not yield gelatine by boiling. 



Elastic tissue is probably developed from 

 cells. In all parts of embryos where elastic 

 tissue occurs, peculiar fusiform or stellate 

 cells (fig. 190 a) with acute ends or pro- 

 cesses are met with, by the fusion of which 

 (tig. 190 b & 191) long fibres or networks 

 are formed, in which the spots correspond- 

 ing to the cells at first form dilatations with 

 elongated nuclei. The fibres frequently 

 remain in this condition, forming a modifi- 

 cation of the so-called nuclear fibres; or 



Fig. 190. 



Fig. 191. 



Fig. 190. Formative cells of elastic tissue, from the 

 tendo Achillis : a, of a four months' embryo b of a 

 seven months' foetus ; some of the cells are free 'with 

 one or two processes, others fused in twos and threes 

 Magnified 350 diameters. 



Fig 191 Stellate formative cells of nuclear fibres, 

 from the tendo Aohillia of a newly born infant. Mae- 

 mfied 350 diameters. 



