THE CONNECTIVE TISSUES. 



79 



According to one view, they are produced from and by the cytoplasm 

 of connective-tissue cells, which, in consequence are often called 

 fibroblasts (Fig. 65). It is difficult to understand how this can be 

 true in all cases, and mucous tissue offers an example of one of 

 these. Another view is that the fibres are formed within the inter- 

 cellular " ground substance " — i. e., the apparently homogeneous 

 material lying between the cells and fibres — as a sort of coagulum or 

 segregation of the substances constituting the fibres. 



Mucous tissue of a rather highly cellular character is abundant 

 in the embryo, where it constitutes an early stage in the development 

 of the fibrous tissues (Fig. 63). A variety less rich in cells forms 



Ftg. 63. 





Embryonic connective tissue (mesenchymatous tissue). (Bohm and Davidoff.) a, nucleus 

 of stellate cell ; b, cytoplasmic process. The intercellular substance is of gelatinous con- 

 sistency and optically bomogeneous. 



the Whartonian jelly of the umbilical cord. It does not occur in 

 the adult under normal conditions, except, perhaps, in the vitreous 

 humor of the eye. 



2. Reticular Tissue (Fig. 64). — The fibres of this variety of ele- 

 mentary tissue are disposed in extremely delicate bundles, which 

 anastomose with each other to form a fine mesh work. The spaces 

 between the fibrous bundles are filled with lymph, which is usually 

 so crowded with cells similar to the white blood-corpuscles that the 

 structure of the tissue is masked by their presence. The cells of 



