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myelencephalon a dorsal coordination zone, and medial and lateral 

 association zones. It is difficult to understand what the author means 

 by these terms. What shall the dorsal zone coordinate, or with 

 regard to what shall the medial zone play the role of association? 

 As the account proceeds it appears that the dorsal zone receives the 

 sensory roots of certain cerebral nerves, viz., the lateralis and part of 

 the acusticus (p. 651), while the association column is the place of 

 ending of the tractus spinalis trigemini, N. vagus, N. glossopharyngeus, 



Fig. 7. Part of a transverse section, right side, sliowing two cells of the somatic 

 sensory column and three fibers of the N. vagus ending in this column. Magn. about 

 80 diam. 



and part of the N. acusticus. In other words, the "coordination" and 

 "association" zones together constitute the sensory centers for the 

 general cutaneous and acustico - lateralis components in the cranial 

 nerves. As the author has not recognized the visceral sensory nerve 

 roots, so the visceral sensory column in the brain has little importance 

 in Tretjakoff's descriptions. It is perhaps (?) represented by his 

 medial association zone. His other zones are roughly equivalent to 

 the acustic centers and substantia gelatinosa trigemini of authors. 

 Tretjakofp seems to assign a large part of the gray matter of 



