96 THE NERVOUS SYSTEM 



the long ascending fibers from the sacral, lumbar, and lower thoracic roots 

 constitute a well-defined medially placed bundle, the fasciculus gracilis, sepa- 

 rated from the rest of the posterior funiculus by the posterior intermediate 

 septum. Those of the long ascending fibers, which finally reach the brain, 

 terminate in gray masses in the posterior funiculi of the medulla oblongata 



Fig. 70. Bifurcation of the dorsal root fibers within the spinal cord into ascending and 

 descending branches, which in turn give off collaterals; the termination of some of these col- 

 laterals in synaptic relation to cells of the posterior gray column. (Cajal, Edinger.) 



(nucleus of the funiculus gracilis and nucleus of the funiculus cuneatus). Since 

 the number of these long ascending branches must increase from below upward 

 it is easy to understand the progressive increase in size of the posterior funiculus 

 from the sacral to the cervical region (Fig. 60). 



The fasciculus gracilis and fasciculus cuneatus are composed for the most 



