THE STRUCTURE OF THE CEREBRUM. 



173 



into one common stem (Figs. 115 and 128). They remain bipolar 

 in the olfactory and acustic ganglia, but form multipolar cells 

 in the sympathetic ganglia. 



Sustentacular Tissue (Fig. 53). In the brain and spinal cord 

 and in the optic nerves two forms of sustentacular tissue are 



Fig- 53- A section through the spinal cord of a human fetus, 23 cm. in length. 

 Showing the central canal with its substantia gelatinosa centralis, neuroglia 

 cells and ependyma cells. (After Lenhossek. Gordinier's Nervous System.) 



found supporting the neurones, viz.: (i) The epiblastic tissue, 

 comprising the neuroglia and the ependyma: (A) Neuroglia 

 is most abundant in gray matter. It is made up of richly branched 

 nucleated cells whose processes form a fine reticulation in the 



