374 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



marks the entrance into the cord of the dorsal roots 

 of the spinal nerves. In a like position, anteriorly, 

 is the exit of the anterior roots of the spinal nerves, 

 but there is no depression or groove as in the case of 

 the posterior roots. The two roots of the spinal 

 nerves divide each half of the spinal cord into three 

 regions or major tracts known as the posterior, 



Posterior horn 

 cell. 



Crossed pyram- 

 idal column. 



Golgi cell ol 

 posterior horn. 



Direct cerebel- 

 lar column. 

 Column cells. 



Golgi's commis- 

 sural cells. 



'owers's column. \ 



Motor cells 



Collaterals 

 ending it 

 the gray 

 matter. 



Direct Pyramidal column. , 



Fig. 265. Schematic diagram of the spinal cord in cross section after 

 von Lenhossek, showing in the left half the cells of the gray matter, in 

 the right half the collateral branches ending in the gray matter (Huber). 



lateral, and anterior columns. The posterior column 

 is limited by the posterior fissure and the posterior 

 roots, the lateral is the region between the roots, 

 and the anterior lies between the anterior root and 

 the anterior fissure. 



Spinal Nerves. Thirty-one pairs of nerves arise 

 from the side of the cord. These are classified into 



