NEUROGLIA 



197 



taxonomic, but a combination of both. It serves, however, to indicate 

 the growth of the cell away from the surface, the moving of its nucleated 

 body toward its internal or proximal end, and its final separation from 

 all connection with the surface. The successive stages of branching as 

 the cell moves away are also easily noted. 



FIG. 175. Four neuroglia cells taken from different sources to show four grades of specializa- 

 tion as connective cells of the nerve tissues. The specialization consists of increasing 

 removal from the surface and the development of branches. Individual figures taken from 

 " STOHR'S Text-book of Histology " by LEWIS. 



The relation is clearer here than in any of the invertebrate tis- 

 sues, where, however, the same truth holds for neuroglia as to its 

 origin and use. 



The most characteristic struc- 

 tural feature of neuroglia tissue is 

 the rather small number of smooth, 

 strong fibrils that the branching 

 cytoplasmic processes of the cells 

 produce. These fibrils are unlike 

 the fibrils of simple binding con- 

 nective tissue in that they are long 

 and of a uniform size and a smooth, 

 even contour. They do not branch 

 as a rule, and are not produced by 

 the cytoplasm of the central mass, 

 but rather by the peripheral por- 

 tions and its processes. The dense 

 branching effect of the neuroglia 

 cell, when stained by the Golgi process, is due to the staining of the 

 protoplasm in which the fibrils lie, as well as the fibrils themselves. 



FIG. 1 76. Part of a section of the spinal cord 

 of a rabbit, gl.c., neuroglia cell; fi., neurog- 

 lia fibrils; conn. I.e., connective tissue cell. 

 (After K. C. SCHNEIDER.) 



