194 



NERVE-CENTRES 



[CH. XVII. 



The majority of nerve-cells found in the body are multipolar. 

 Here the cell becomes angular or stellate. Fig. 207 shows the usual 

 form of cell present in sympathetic ganglia. From the angles of the 

 cell, branches originate ; the majority of these branches divide and 

 subdivide until each ends in an arborescence of fine twigs or fibrils ; 



N.S. 



Fro. 206. Bipolar nerve-cells. A. From the Gasserian ganglion of the pike (after Bidder). B. From a 

 " :s" human embryo (after His). C. Adult condition of the mammalian 



spinal ganglion of a 4 weeks' 



spinal ganglion cell : N. S. nucleated sheath ; only the nuclei seen in profile are represented. 



the T-shaped junction (after Retzius). 



T. is 



but one process, and one process only, of each cell becomes the axis 

 cylinder of a nerve-fibre. 



Passing next to the central nervous system, we here again find 

 the multipolar cell is the principal kind present. 



The next figure (fig. 208) shows one of the typical multipolar cells 

 of the spinal cord. Here again, only one process (a) becomes the 

 axis cylinder of a nerve-fibre, and the others break up into arborisa- 

 tions of fibrils. The cells have a finely fibrillar structure, and the 

 fibrils can be traced into the axis cylinder process and the other 

 branches of the cell. Between the fibrils the protoplasm of the cell 



