474 



THE ORGANS 



probably lie in the ventro-lateral columns, though some authorities 

 place them in the dorsal columns. 



This pallio-bulbo-spino-sympathetic path is the path by which various 

 psychic states (emotions, perceptions, memories) affect the splanchnic effectors, 

 as seen in blushing, perspiring, erection, pupillary changes, etc. 



Many tracts contain fibres proceeding in a direction opposite to that of most 

 of the fibres. 



Fundamental Columns or Ground Bundles (Shorter Inter- 

 segmental Tracts of Cord or Spino-spinal Tracts) 



The ascending and descending tracts above described are known 

 as the long-fibre tracts of the cord. If the area which these tracts 

 occupy be subtracted from the total area of white matter, it is seen 

 that a considerable area still remains unaccounted for. This area 

 is especially large in the antero-lateral region, and extends up along 



Receptor 



Fig. 328. — -Diagram illustrating a Two-neurone Spinal Reflex Arc. Groups of neu- 

 rones are represented by one neurone, gg, Spinal ganglion. (Van Gehuchten.) 



the lateral side of the posterior horn between the latter and the crossed 

 pyramidal tract (Figs. 319 and 326). A small area in the posterior 

 column just dorsal to the posterior commissure, and extending up a 

 short distance along the medial aspect of the horn, should also be 

 included. These areas are occupied by the fundamental columns or 

 short-fibre (spino-spinal or proprio-spinal) systems of the cord. The 



