TISSUES, ORGANS, AND SYSTEMS. 



63 



Physiologically, the prominent characteristic of this tissue is 

 its elasticity, in consequence of which it forms a most essential 

 support to the motor organs, and also plays an important part 

 in other situations, e. g. in the 

 vocal ligaments. With respect 

 to its development, the supposition 

 of Schwann, that this tissue pro- 

 ceeds from cells, receives increas- 

 ing support from modern investi- 

 gations; in fact, in all those organs 

 which subsequently contain elastic 

 tissue, there may be discovered 

 in embryos, peculiar fusiform 

 or stellate, sharply-pointed cells, 

 which by their coalescence pro- 

 duce long fibres or reticulations, 

 in which at first, those localities 

 where the bodies of the cells pre- 

 viously existed may still be recog- 

 nised as enlargements containing 

 elongated nuclei in their interior. 

 In this condition the fibres not 

 unfrequently remain, and they 

 then form a modification of what 

 were formerly called nucleus-fibres, or every trace of their pre- 

 vious composition disappears, so that quite homogeneous fibres 

 or fibrous reticulations are produced. These may then either 

 remain through life as fine elastic fibres and networks, or by 

 increasing in thickness they may pass into the coarser form 

 of the tissue. The more homogeneous elastic membranes 

 are nothing but close elastic networks, whose fibres have so 

 much increased in diameter, that only narrow spaces remain 

 between them. The perfect elastic tissue appears to undergo 

 very little change of substance — at least it is, so to speak, 

 non-vascular, even when it occurs in large masses; on 



Fig. 26. Formative cells of the elastic fibres, x 350, from the tendo-achillis : 

 a, of a four months' embryo; b, from a seven months' fcetus, — a few cells free, with 

 one and two processes, others united by twos and threes. 



Fig. 27. Stellate formative cells of the nucleus fibres out of thetendo-Achillis of a 

 new-born infant, x 350. 



