ELASTIC TISSUE. 



[ 223 ] 



ELATERS. 



1-2200" or even more ; the lines have been 

 termed nuclear-fibres by the Germans ; they 

 are either isolated, arranged in bundles, or 

 branching and anastomosing (fig. 192) ; 

 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. 



They are easily distinguishable from fibres 

 of areolar 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. 192), or plates perfo- 

 rated irregularly by holes fenestrated 

 membranes (fig. 191). The fibres are also 

 themselves sometimes transversely perforated 

 by irregular rounded apertures. 



Fig. 193. 



Fig. 194. 



' 



Fig. 193. Formative cells of elastic tissue, from the 

 tendo-Achilles ; 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. Magni- 

 fied 350 diameters. 



Fig. 194. Stellate formative cells of nuclear fibres, from 

 the tendo-Achilles of a newly-born infant. Magnified 

 350 diameters. 



The chemical composition of elastic tissue 



has not been accurately determined; it 

 appears rather referable to the proteine than 

 the gelatine group of compounds. It is 

 coloured red by Millon's test, but not by 

 that of Pettenkofer; it does not yield 

 gelatine by boiling. 



Elastic tissue is developed from cells. In 

 all parts of embryos where elastic tissue 

 occurs, peculiar fusiform or stellate cells 

 (fig. 193 a) with acute ends or processes are 

 met with, by the fusion of which (figs. 193 b 

 & 194), long fibres or networks are formed, in 

 which the spots corresponding to the cells at 

 first form dilatations with elongated nuclei. 

 The fibres frequently remain in this condi- 

 tion, forming a modification of the so-called 

 nuclear-fibres ; or all traces of the original 

 composition vanish, uniform fibres or net- 

 works alone remaining. There is, however, 

 still some difference of opinion among phy- 

 siologists as to the development of elastic, as 

 well as of areolar tissue. 



Elastic tissue occurs in the same situations 

 in all classes of the Vertebrata as in man, 

 also in some special localities, as in the 

 ligaments of the claws of the cat, the folds 

 of the wing-membrane, and the pulmonary 

 sacs of birds. In the Invertebrata, this 

 tissue appears to occur but rarely, and it is 

 uncertain whether the elastic ligaments 

 existing in them, e.g. those of the mollusca, 

 agree anatomically and chemically with the 

 elastic tissue of the higher animals or not. 



BIBL. Kolliker, Gewebelehre d. Mensch. 

 p. 45 (and the BIBL. of that article); see also 

 CHEMISTRY. 



ELATERS. This name is applied to two 

 forms of structure occurring in the higher 

 Cryptogamous Plants. The elliptical spores 

 of the Equisetaceae are furnished with what 

 are called elaters, viz. four elastic filaments, 

 attached about the middle of one side, which 

 are coiled once or twice round the spore before 

 it is discharged from the capsule, in the po- 

 sition where they were originally developed; 

 but when the spore is discharged, they un- 

 coil with elasticity, causing the spore to be 

 jerked away. They appear to be produced 

 by the outer coat of the spore splitting in 

 spiral fissures, and separating in ribands from 

 the inner coat. See EQUISETACEAE. 



The elaters of the Liverworts orHepaticacea3 

 are of different nature ; they consist of more 

 or less elongated delicate membranous tubes, 

 which are closed cells, inside which one or 

 more elastic spiral fibres are coiled up. They 

 occur mixed with the spores in the capsules 

 of the Jungermanniese, sometimes attached 



