476 



THE NERVOUS SYSTEM. 



and some passing into the posterior cornu. When the fibers of 

 the posterior root enter the cord they bifurcate, one branch passing 

 upward, the other downward. From the main fiber, and also from 

 the branches, pass collaterals, which end in the gray matter in 

 arborization, and in the nerve-cells of the anterior and posterior 

 cornua. In the same manner end the main fiber and its branches ; 

 some, however, pass upward in the posterolateral and posteromesial 



FIG. 276. Transverse section through half the spinal cord, showing the ganglia : 

 A, anterior cornual cells ; 5, 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, rarnus communicans ; H, posterior 

 branch of spinal nerve ; J, 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 (d) process 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 ; </, fiber of the anterior root terminating by an arborization in the sympa- 

 thetic ganglion ; h, sympathetic fiber passing to periphery (Ramon y Cajal). 



columns, and end in the medulla by arborizing around the cells of 

 the nucleus gracilis and cuneatus. 



Spinal Ganglia. The structure of these ganglia has been 

 already described. Beyond the ganglion the two roots unite to 

 form the trunk of the spinal nerve, which passes out through the 

 intervertebral foramen, and gives off a recurrent branch to the 

 dura mater of the cord. It then divides into a posterior division, 

 which is distributed to the posterior part of the body,, and an ante- 



