406 PHYSIOLOGY 



cross over in the pyramidal decussation to run down in the crossed 

 pyramidal tract on the other side of the cord. The few fibres which 

 do not cross over in the pyramidal decussation are continued as the 

 direct or anterior pyramidal tract. These, however, also cross to the 

 other side in their passage down the cord before becoming connected 

 with the anterior cornual cells. Hemisection therefore of the spinal 

 cord in the dorsal region will produce paralysis of motion and loss 

 of or impaired sensation in the parts supplied by the nerves on the 

 same side below the lesion. 



A great part of the white matter of the cord is concerned then in 

 maintaining connection between the brain and higher parts of the 

 nervous system and the periphery, through the intermediation of the 

 cells of the grey matter of the cord. Corresponding to this function 

 we find a gradual increase in the number of fibres in the white matter as 

 we ascend from the sacral part of the cord to the medulla, the white 

 matter being continually reinforced as it ascends the cord by fibres 

 establishing connection with the ganglion- cells forming the nuclei of 

 the nerve-roots. 



Vaso-motor impulses to the limbs travel down the lateral columns 

 of the cord on the same side. 



