THE CEREBELLUM 



519 



Those portions of the cortex which are thus carried in with the 

 sulci are necessarily attenuated. 



The cells of Purkinje form the characteristic element of the 

 cerebellar cortex. These are very large pyrif orm nerve cells, placed 

 between the nuclear and the molecu- 

 lar layers, with their long axis nearly 

 perpendicular to the adjacent surface 

 of the convolutions. From their in- 

 ner pole a neuraxis arises, and, pene- 

 trating the nuclear layer, enters the 

 white medulla, where it acquires a 

 medullary sheath. In its passage 

 through the nuclear layer the neur- 

 axis gives off recurrent collaterals 

 which return into the molecular layer 

 to terminate in relation to neighbor- 

 ing cells of Purkinje. 



A thick-stemmed dendrite arises 

 from the outer pole of the Purkinje 

 cell, but immediately divides into two 

 primary branches. Occasionally the 

 two branches are given off directly 

 from the cell body. From these pri- 

 mary branches smaller processes pass 

 into the molecular layer and dicoty- 

 mously divide into an innumerable 

 number of fine terminal fibrils. This 

 arborization is peculiar in the absence 

 of anastomoses, and in the fact that 

 it lies entirely within the limits of a 

 plane whose diameter is no greater 

 than that of the cell body, a plane 

 which is found in the transverse axis 

 of the cerebellar convolution. It is 

 therefore impossible to demonstrate 

 this arborization in sections which 

 are cut parallel to the long axis of 

 the convolution. The bodies of the 

 Purkinje cells are closely surrounded 



by a basketwork of terminal fibrils derived from the cells of the 

 molecular layer. 



FIG. 402. A PURKINJE CELL FROM 



THE CEREBELLAR CORTEX OF 

 THE RABBIT. 



Highly magnified. (After Nissl.) 



