THE NERVOUS SYSTEM 1375 



The inferior mediillan^ velum forms a part of the lobus m duli, the 

 other parts, as stated, being the nodule and the two floccuh. 



Minute Structure of the Cerebellar Laminae. — Each lajnina or 

 foHum of the cerebellmri consists of (i) a central part or core of 

 white matter, which is an offshoot from the white medullary sub- 

 stance, and (2) an external part or cortex of grey matter. 



Grey Cortex. — The grey cortex is composed of two layers, an 

 outer molecular layer, and an inner granular layer. Between these 

 two layers there is a stratum of characteristic large cells, called the 

 cells or corpuscles of Purkinje. 



The cells of Purkinje are pyriform or flask-shaped, and are 

 situated, as just stated, between the molecular and granular 

 layers. The narrow or superficial end of each cell projects into 

 the molecular layer, and the broad or deep end rests on the 

 granular layer. From the broad or deep end of each cell a single 

 axon passes off, which enters the granular layer, where it soon 

 becomes meduUated, and then forms a ner\^e-fibre of the white 

 medullary substance. The axon of Purkinje's cell gives off a few 

 collateral recurrent branches, some of which end in the granular 

 layer, whilst others enter the molecular layer. 



From the narrow or superficial end of each cell one or two den- 

 drons are given off. These divide and subdivide at frequent 

 intervals in the molecular layer ' like the antlers of a deer.' The 

 dendritic processes so formed are arranged in an arborescent 

 manner, and are distinct from those of adjacent cells. They per- 

 meate the molecular layer as far as the surface. 



The molecular layer consists of a few nerve-cells and many nerve- 

 fibres. 



The nerve-cells are situated partly in the inner or deep portion 

 of the molecular layer, and partly in its outer portion. 



The inner cells are known as the hashet-cells, and they lie in the 

 vicinity of the cells of Purkinje. Each basket-cell has several 

 dendritic processes which ramify in all directions. In addition to 

 these processes there is an axon, which springs from the side of the 

 cell and takes a transverse course. It gives off a number of col- 

 laterals which pass towards the bodies of the cells of Purkinje. 

 These collaterals terminate by ramifpng ver}^ freely aroimd the 

 cells of Purkinje, as well as around the axons of these cells for a 

 short distance. The minute terminal ramifications form a close 

 basket-work, which encloses the cell of Purkinje and its axon for a 

 short distance. 



The outer cells of the molecular la\'er are small, and each has 

 several dendritic processes and an axon. Each axon springs from 

 the side of the cell, and, taking a transverse course, it ends in 

 numerous ramifications. 



The fibres of the molecular layer are derived from the following 

 sources: (i) The dendritic processes, and the recurrent collaterals 

 of the axons, of the cells of Purkinje; (2) the dendritic processes 

 and axons of the outer cells ; (3) the dendritic processes of the inner 

 or basket-cells; (4) the axons of the granule-cells of the granulai 



