THE SPINAL NERVES 



297 



traced to the anterior cornu of gray matter and a posterior 

 which goes (apparently) to the posterior cornu and these 

 emerge respectively from the antero-lateral and postero-lat- 

 eral fissures of the cord. .Before leaving the spinal canal 

 these two roots join to pass through the corresponding in- 

 tervertebral foramen as a single trunk which, however, just 

 beyond that foramen divides into anterior and posterior 



B. 



FIG. 87. 



A, bipolar cell from spinal ganglion of a 4% weeks' embryo (after His), n, 

 nucleus; the arrows indicate the direction in which the nerve processes grow, 

 one to the spinal cord, the other to the periphery. B, a cell from the spinal gan- 

 glion of the adult; the two processes have coalesced to form a T-shaped junc- 

 tion. (Kirkes.) 



branches to be distributed to the anterior and posterior parts 

 of the body. 



The posterior root (inside the spinal canal) is sensory, 

 and has a ganglion developed upon it. The fibers of the 

 posterior root are outgrowths of cells in the ganglion of that 

 root, as indicated in Fig. 87. This accounts for the arborisa- 

 tion of the different fibers around cells in the cord instead 

 of an actual connection with them. These facts should not 

 be lost sight of though it is customary to speak of an efferent 



