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THE NERVOUS SYSTEM 



perimentally, decussation of sensory fibers is demonstrated (i) by 

 longitudinal section of the spinal cord in the median line, which 

 is followed by anesthesia on both sides below the section; and (2) 

 by horizontal section of one-half of the cord, which is followed 



FIG. 78. Transverse section through half the spinal cord, showing the 



ganglia. 



A, anterior cornual cells; B, axis-cylinder process of one of these going to posterior 

 root; C, anterior (motor) root; D, posterior (sensory) root; E, spinal ganglion on 

 posterior root; F, sympathetic ganglion; G, ramus communicans; H, posterior branch 

 of spinal nerve; I, anterior branch of spinal nerve; a, long collaterals from posterior 

 root fibers reaching to anterior horn; b, short collaterals passing to Clarke's column; 

 c, cell in Clarke's column sending an axis-cylinder process (d) to the direct cerebellar 

 tract; e, fiber of the anterior root;/, axis cylinder from sympathetic ganglion cell, 

 dividing into two branches, one to the periphery, the other toward the cord; g, fiber 

 of the anterior root terminating by an arborization in the sympathetic ganglion; h, 

 sympathetic fiber passing to periphery. (Kirkes after Ramony Cajal.) 



by anesthesia on the opposite side below the section. It is 

 claimed that pain and temperature sensations decussate at once 

 on reaching the gray matter, while sensations of touch, pressure 

 and equilibration pass up on the same side until the medulla is 



