208 



THE NERVOUS SYSTEM 



almost at once becomes myelinated and runs through the granular layer into the 

 white substance of the cerebellum. According to Clarke and Horsley (1905) and 

 Cajal (1911) these axons end in the central cerebellar nuclei. Near their origin 

 they give off collaterals, which run backward through the molecular layer to 

 end in connection with neighboring Purkinje cells an arrangement designed 

 to bring about the simultaneous discharge of a whole group of such neurons. 

 The granular layer, situated immediately subjacent to that which we have 

 just described, is characterized by the presence of great numbers of small neurons, 

 the granule cells. Each of these contains a relatively large nucleus, surrounded 

 by a small amount of cytoplasm; and from each there are given off from three 

 to five short dendritic branches with claw-like endings. These are synaptically 

 related with the terminal branches of the moss fibers, soon to be described, and 



Purkinje cell" 



Basket cell" 



Granule cell " 



"Purkinje cell 

 ' Granule cell 



Fig. 151. Diagrammatic representation of the structure of the cerebellar cortex as seen 

 in a section along the axis of the folium (on the right), and in a section at right angles to the axis 

 of the folium (on the left). 



form with them small glomeruli comparable to those of the olfactory bulb (Fig. 

 208). Each granule cell gives origin to an unmyelinated axon, which extends 

 toward the surface of the folium and enters the molecular layer. Here it divides 

 in the manner of a T into two branches. These run parallel to the long axis of 

 the folium through layer after layer of the dendritic expansions of the Purkinje 

 cells, with which they doubtless establish synaptic relations (Fig. 151). Besides 

 the granules just described, this layer contains some large cells of Golgi's Type 

 II (Fig. 150, /). Most of these are placed near the line of Purkinje cells and 

 send their dendrites into the molecular layer, while their short axons resolve 

 themselves into plexuses of fine branches in the granular zone. 



The molecular layer contains few nerve-cells and has in transverse sections 

 a finely punctate appearance. It is composed in large part of the dendritic 

 ramifications of the Purkinje cells and the branches of axons from the granule 



