,380 ANATOMY FOR NURSES [Chap. XIX 



downward ; they begin in the gray matter of the brain, descend, 

 and terminate in the gray matter of the cord. The most im- 

 portant tracts are : — 



Postero internal tract or Cohimns of Goll. 

 Ascending or Postero external tract or Columns of Burdach. 

 Sensory Antero lateral tracts. 



Postero lateral tracts. 

 Descending or f Crossed pyramidal tract. 

 Motor \ Direct pyramidal tract. 



In addition to these long tracts, there are shorter columns con- 

 sisting of both sensory and motor nerves, which serve to connect 

 centres at different levels in the cord, and on different sides of the 

 cord. These are called lateral columns. 



SPINAL NERVES 



There are thirty-one pairs of spinal nerves, arranged in the 

 following groups, and named from the region through which they 

 pass. They are : — 



Cervical 8 pairs. 



Thoracic 12 pairs. 



Lumbar 5 pairs. 



Sacral 5 pairs. 



Coccygeal 1 pair. 



The first cervical nerve arises from the medulla oblongata and 

 leaves the neural canal between the occipital bone and the altas. 

 With this one exception the spinal nerves spring from both sides 

 of the spinal cord, and with one exception — coccj^geal — they 

 pass out through the intervertebral foramina. The coccyxgeal 

 passes through the lower extremity of the canal. 



Mixed nerves. — The spinal nerves consist almost entirely of 

 medullated nerve-fibres, and are called mixed nerves because they 

 contain both sensory and motor fibres. Each spinal nerve has two 

 roots, a ventral or anterior root and a dorsal or posterior root. 

 The fibres connected with these two roots are collected into one 

 bundle, and form one nerve just before leaving the canal through 

 the intervertebral openings. Before joining to form a common 



