NORMAL HISTOLOGY. 



within the outer layer, while those of the larger cells divide within 

 the granule layer ; in both cases, it will be remarked, the axis-cylinder 

 processes terminate entirely within the gray matter, thus identi- 

 fying their possessors as nerve-cells of the second type. In 

 addition to the nervous elements, a few flattened cells, with feebly- 

 developed processes, are scattered throughout the granule zone ; 

 these are to be regarded as belonging to the supporting frame- 

 work. The interstices between the numerous nerve-cells are partly 

 occupied by the plexus of medullated nerve-fibres which are 

 derived from the bundles of parallel fibres continued from the medul- 

 lary tracts ; some of these fibres pass beyond the nuclear layer to 

 end within the molecular zone. 



The cells of Purkinje form the thinnest but, at the same time, 

 the most characteristic layer of the cerebellar cortex. These ele- 

 ments, among the largest ganglion-cells in the body, are disposed as 

 a single row at the junction of the nuclear and the molecular layer, 

 and present pyriform or flask-shaped bodies, 60-70 n in their longest 

 diameter, placed vertically to the plane of the zone, with the larger, 

 rounded end resting on the outer margin of the nuclear layer, while 

 the smaller end is directed towards the periphery. Each cell pos- 

 sesses a large nucleus (15 >JL) as well as a nucleolus, and differs 

 from other ganglionic elements in containing little or no pigment. 

 The central pole is prolonged as the axis-cylinder process, which, 

 after giving off collateral fibres, passes on to become the axis-cylinder 

 of a medullated nerve. The most distinctive feature of these cells, 

 however, is the distribution of their protoplasmic processes. 

 A thick tapering process, usually single, but occasionally double, 

 extends from the small end of the flask-shaped body towards the 

 periphery ; this stem very soon divides into two, the branches run- 

 ning horizontally, sometimes almost at right angles to the parent 

 stalk before turning towards the surface ; the peculiarity of the rich 

 ramification which follows is the dominating vertical direction of the 

 larger branches. While the pictures presented by the cells of Pur- 

 kinje in successfully-stained sections have always been among the 

 most striking, it was not until the introduction of Golgi's silver 

 method that a full appreciation of the remarkable richness of these 

 ramifications became possible. In such preparations the molecular 

 layer is occupied to its extreme periphery by the intertwining but 

 ununited fibrils of the branching processes. The extent and 

 breadth of these apparent net-works, however, vary with the point 

 of view, for the cells send out their branches especially in a direction 

 at right angles to the long axis of the convolution or the medullary 

 tract, while in a plane parallel to this axis the branches are limited 

 to a narrow zone, scarcely wider than the body of the cell : it follows 



