24 



ANATOMY OF THE CENTEAL NEHVOTJS SYSTEM. 



actual contact with them. These fibrillas are in part collaterals from a tract 

 which we know from observations in pathology passes from large cells in 

 the brain-cortex downward through the brain and spinal cord. This tract 

 — which consists again of brain-cell, descending nerve, collaterals, and 

 ramifications — is adapted to the establishment of a connection between the 

 brain, and the end-plates in the muscles; it is the central segment of the 

 motor course of innervation, or, at least, a part of it. This is the motor tract 

 of the second order. How many of these units are involved in a complete 

 motor process is as yet unknown. In Fig. 152 one observes that the ramified 



Fig. 7.- 



-Sohematic representation of the relation of ganglion-cell and 

 nerve in u. motor tract. 



neuraxons of other cortical cells surround the dendrites of those large corti- 

 cal cells from which the secondary motor tract originates. These represent 

 tracts of higher order. 



Work on the inner structure of ganglion-cells, for the revival of which 

 we are especially indebted to Nissl, has not yet led to conclusive results, 

 especially because the significance of the fine lines which appear after treat- 

 ment with sublimate, alcohol, and basic anilin stains is not yet clear; also 

 because it is not yet always certain how much these structural features may 

 depend upon the influence of the reagents themselves. JSTevertheless, the 

 work of Nissl, who especially advised fixation with alcohol, has led to very 



