30 



THE ESSENTIALS OF HISTOLOGY 



kinds white and yellow or elastic. Moreover, there are many points 

 of similarity between the cells which occur in these several tissues ; 

 they are also developed from the same embryonic formation, and they 

 tend to pass imperceptibly the one into the other. Besides this, 

 their use is everywhere similar ; they serve to connect and support 

 the other tissues, performing thus a passive mechanical function. 

 They may therefore be grouped together, although differing consider- 

 ably in external characters. Of these connective tissues, however, 

 there are three which are so intimately allied as to be naturally con- 

 sidered together, being composed of exactly the same elements, although 

 differing in the relative development of those elements ; these are the 

 areolar, elastic, and fibrous tissues (adipose tissue may be looked upon 

 as a special modification of areolar tissue). Areolar tissue being the 

 commonest and, in one sense, the most typical, its structure may be 

 considered first. 



Areolar tissue. The areolar tissue presents to the naked eye an 

 appearance of fine transparent threads and laminae which intercross in 

 every direction with one another, leaving intercommunicating meshes, 

 or areolae, between them. When examined with the microscope, these 

 threads and fibres are seen to be principally made up of wavy bundles 

 of exquisitely fine transparent fibres (white fibres, fig. 30). The bun- 

 dles run in different directions, and may branch and intercommuni- 

 cate with one another ; but the individual fibres, although they pass 

 from one bundle to another, never branch or join other fibres. The 



FIG. 31. GROUND SUBSTANCE OF 

 CONNECTIVE TISSUE STAINED 

 BY SILVER. (The cell-spaces 

 are left white.) 



FIG. 30. BUNDLES OF THE WHITE FIBRES OF 

 AREOLAR TISSUE PARTLY UNRAVELLED. 



fibres are cemented together into the bundles by a clear substance 

 containing mucin, and the same clear material forms also the basis or 

 ground-substance of the tissue, in which the bundles themselves course, 

 and in which also the corpuscles 'of the tissue lie embedded. This 



