7 8 CELL DIFFERENTIATION AND THE ELEMENTARY TISSUES 



THE NEUROGLIA. 



The neuroglia, while not a nervous tissue, is closely mingled with it and 

 forms an important constituent of the nervous system. It consists of cells 

 giving off a fine network of richly branching fibers. Neuroglia is a form 

 of connective tissue, and it is in its functions strictly comparable to the con- 

 nective tissue which supports the special structures of other organs, like the 

 lungs and kidneys, figure 106. In the adult animal the neuroglia tissue is 



FIG. 1 06. Different Types of Neuroglia Cells. (After Van Gehuchten.) b, Neuroglia 

 cells of the white substance, and c, of the gray substance of the cord of an embryo calf. 



composed of cells from which are given off immense numbers of fine proc- 

 esses. These extend out in every direction, and intertwine among the nerve 

 fibers and nerve cells, figure 105. The neuroglia cell differs in size and shape 

 very much in different parts of the nervous system in accordance with the 

 arrangement of the nervous structures about it. The cell is composed of 

 granular protoplasm, and lying in it is a large nucleus, within which is a 

 nucleolus. The body of the cell is small in proportion to the nucleus. 



