THE PROBLEM OF NEURON PATTERN 



163 



external surface of the cortex and its growth is directed 

 away from the surface (A). The chief dendrite appears 

 at the opposite end of the cell and its growth is directed 

 toward the surface (B, C); as the axon elongates, 



I 



ABC 



D 



55 



54 



FIGS. 54, 55. Fig. 54, development of the pyramidal neuron (from 

 Cajal, 191 1); Fig. 55, Purkinje cell from cerebellum of new-born infant 

 (from Cajal, 1911). 



collateral branches arise from it and grow more or less 

 vertically to its direction (D); and still later dendrites 

 arise from various parts of the cell surface and grow in 

 various directions (). Taking the cell at the stage 

 B or C it appears that axon and dendrite are localized 



