214 THE NERVOUS SYSTEM. 



aspect (that directed toward the surface) give off coarse proto- 

 plasmic processes which divide and subdivide (in narrow 

 transverse planes) into extensive arborizations occupying the 

 entire thickness of the molecular layer; from the deeper 

 aspect each cell gives off an axis cylinder process which passes 

 inward through the nuclear layer. 



The mokcular layer is the superficial stratum of the cere- 

 bellar cortex, and consists chiefly, besides neuroglia, of the 

 extensive interlacing ramifications of the dendrites of the cells 

 of Purkinje and of the processes of other nerve-cells in the 

 vicinity. This layer also contains scattered small multi polar 

 nerve-cells ; the neurites of some of these cells (" basket cells") 

 run parallel to the surface and give off branches which break 

 up into terminal basket-like networks of fibrils that surround 

 the bodies of Purkinje's cells. 



The Spinal Cord. 



The spinal cord is divided into symmetrical lateral halves by 

 the deep and narrow posterior median " fissure " (really a 

 fibrous septum) and the broad but shallower anterior median 

 fissure. 



The periphery of the cord is formed by white matter, con- 

 sisting of a dense mass of longitudinal medullated nerve- 

 fibres, supported by neuroglia and narrow connective-tissue 

 extensions from the pia mater passing radially inward. The 

 narrow layer of white matter intervening between the gray 

 commissure and the fundus of the anterior median fissure con- 

 stitutes the "anterior" or "white commissure." 



From physiological and pathological considerations the 

 white fibres of the cord are divisible into definite longitudinal 

 tracts, but these divisions are only partially apparent to sight 

 in the normal cord (Fig. 84). 



The interior of the cord is occupied by gray matter, which 

 consists of two lateral parts, curved outward, joined by a 

 transverse portion (the "gray commissure"), thus in cross- 

 section roughly exhibiting an H shape. 



The gray matter is composed of neuroglia, interlacing den- 

 drites, nerve-fibres (with and without medullary sheaths), and 

 nerve-cells. 



