CENTRAL ORGANS OF NERVOUS SYSTEM. 223 



tical fibres of the white columnar system. These cell groups 

 were accordingly a provisory centre. 



The further communications of the ganglion bodies, of the 

 equivalent between each other, as well as of the motory with 

 the sensory cells, are up to the present time veiled in the 

 deepest obscurity. 



Let us mention, finally, in the uncertainty of our knowl- 

 edge, the transverse commissures of the spinal cord. The 

 anterior shows true nerve fibres in the most distinct manner. 

 The bundles of the same arise from the gray substance of the 

 one half (without our knowledge of the manner of their ori- 

 gin), to ascend and descend and gain the fibrous mass of the 

 anterior column at the other side. An endeavor has been 

 made to deduce from this a total decussation of the motory 

 tract of our organ. 



The posterior commissure also contains, together with con- 

 nective-tissue constituents, bundles of fine nerve fibres. 



