ANATOMY OF THE NERVOUS SYSTEM. 



181 



made of greatly branched cells (Fig. 83), and named the 

 neuroglia or sus tentacular tissue. 



Nerve-Centres consist of white and gray nerve-fibres, of 

 nerve-cells, of neuroglia, and 

 of connective tissue and 



blood-vessels arranged in -^^W^l^&tiM'hln 

 different ways in the differ- 

 ent centres. They are es- 

 sentially collections of nerve- " v \j/ \&M 7*\/$r^n. 



FIG. 82. A thin section of the cere- FIG. 83. Cells from the surface gray mat- 

 bellum showing: pear-shaped cells of ter of a cerebral convolution : p, nerve-cells 

 Purkinje, and numerous other small with axis cylinder processes, o ; ?i, non-ner- 

 nerve-cells. vous neuroglia cells. The method of prepa- 



ration (Qolgi's) stains the cells an uniform 

 black. 



cells and nerve-fibres, some of the latter being connected with 

 the cells, while others may merely pass through on their way 

 to or from other centres. As an illustration of the structure 

 of a more complex nerve-centre we may study the spinal cord. 

 Histology of the Spinal Cord. If a thin transverse sec- 

 tion of the spinal cord be examined with a microscope it will 

 be found that enveloping the whole is a delicate layer of 

 connective tissue, the pia mater. Fine bands of it ramify 



