NERVOUS SYSTEM. 29 



the place where the ventral root of the spinal nerve arises. 

 This part of the gray matter is called the ventral horn of 

 the gray matter. If this portion be examined under a 

 moderately high power of the microscope, there may be 

 seen a number of cells with radiating branches. 



Dorsal or Sensor 

 Root 



Ganglion 



i 



Ventral or Motor Root 



Fig. 1 1 . Cross-section of Spinal Cord. 



Functions of the Spinal Cord. The spinal cord has 

 two main functions : 



1. Its conducting power, by means of the white fibers 

 which make up the outer part of the cord. These fibers 

 may be regarded as connecting the gray matter of the 

 brain with all parts of the body. 



2. The gray matter is the center of the reflex actions of 

 the cord. 



Ganglia. Masses of nerve cells make up nerve centers, 

 or ganglia, such as are on the dorsal roots of the spinal 

 nerves. These also would show under the microscope 

 that their chief constituent is a collection of nerve cells 

 which give off one or more branches. 



