5i{ HISTOI.<H;Y. , 



and anastomose with one another to form a network. They arc 

 characteri/ed by being highly refractive and elastic. If we 

 act upon white fibrous tissue witli acetic acid or alkalies, the 

 fibrils swell up. and on this uniform background the twisted or 

 spiral course of the elastic fibres is often brought out with 

 great distinctness, for the latter are not affected by these 

 reagents. The elastin of which the elastic fibres consist is 

 characterized in general by a resistance to ordinary reagents. 

 Acids and alkalies do not affect it. Digestion in pepsin and 

 boiling in water and dilute acids or alkalies are all resisted. It 



FIG. 30. 



\Vhit- connective-tissue fibrils from ;i tendon of the mouse, treated with picric acid and 

 teased out with needles. SIX). 



digests, however, in pancreatin. When a great many of these 

 elastic fibres occur together, we speak of them as elastic iisxuc 

 (see below ). 



(7) The ground substance in which these fibres are laid 

 down is quite homogeneous, and in definitely developed connec- 

 tive tissue is present in very small quantities. 



(2) Cells. In the ground substance between the fibres we find 

 a considerable number of cells. Two main sorts can be distin- 

 guished, namely, the Ji.ml connective-tissue cells, which have no 

 power of motion, and the wand < run/ cells, which can move from 

 one place to another. This division is not definite, because 



