SPINAL CORD. 



35 



matter of the nervous system is made up of nerve fibers whose 

 structure and use we have just considered. But the gray mat- 

 ter has a different structure and a different function. Instead 

 of being made up mainly of fibers, it is composed of cells, 

 rounded masses, some of the forms of which are represented in 

 Fig. 13. Some of the branches of these cells are continued, 

 and become the axis-cylinders of nerves, and it is asserted 



Dorsal Septum 



Dorsal or 

 Sensor 

 Root 



Ganglion- 



Spinal Nerve Ventral or 

 Motor Root 



Fig. 12. Cross-section of Spinal Cord. 



that every nerve fiber begins as a branch of some nerve-cell. 

 One of. the best places to see these nerve-cells is in the 

 gray matter of the spinal cord, near 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 micro- 

 scope, there may be seen a number of cells with radiating 

 branches. 



