iv GEXEKAL PHYSIOLOGY OF NEKVOUS SYSTEM 181 



network more particularly in certain parts of the central nervous 

 system, e.g. the fascia dentata of the hippocampus (Fig. 118) 

 and the cerebellar cortex (Fig. 119). 



The neurone theory, on the other hand, harmonises perfectly 

 with the embryological observations of His (1887), who believed 



FIG. 118. Fascia dentata of pes hippocampi major. (Golgi.) Between the processes coming from 

 the upper layer of nerve-cells and the lower of nerve-fibres there is an intervening zona reticularis 

 composed of nerve-fibres which interlace repeatedly, so that they lose their individuality and 

 constitute what Golgi calls the diffuse nerve network. 



that he had demonstrated the genesis of the nerve elements from 

 the special germinal cells of ectodermal origin, which are inter- 

 posed between the epithelial cells of which the walls of the 

 primitive neural tube are composed. A-polar and rounded in 

 an early stage, they subsequently become piriform; next they 

 send out a nerve process and become uni-polar; finally the 

 dendrites appear also (Fig. 116, a, I, c, d, e). During their growth 



N 2 



