THE SPINAL COED 599 



The ventral white column is included between the ventral median 

 sulcus and the ventral gray horns and nerve roots; the lateral columns 

 extend from the ventral roots in front, around the lateral surface of 

 the spinal cord, to the dorsal roots; the dorsal columns are included 

 between, the dorsal horns of gray matter and dorsal nerve roots, and the 

 dorsal median septum. 



Each of these columns of white matter is again subdivided by 

 neurogliar septa of variable size and number, which extend inward 

 from the pia mater for a considerable distance. Such septa may even 

 penetrate all the way to the central gray matter. One of these septa, 

 the paramedian septum, more constant than the others, subdivides the 

 dorsal column into two portions, a dorsomedial and a dorsolateral 

 column, or the funiculus gracilis (column of Goll), and the funiculus 

 cuneatus (column of Burdach) of the upper portions of the cord. 



In the ventral white column two chief fiber tracts are recognized: 

 a narrow median, the anterior or direct pyramidal tract; and a more 

 lateral larger anterior ground bundle. In the lateral column four main 

 tracts are recognized : three lateral, including an upper crossed pyram- 

 idal tract, a middle direct cerebellar tract, and a lower or Gower's 

 column; and a large medial lateral ground bundle (Fig. 518). These 

 tracts .do not possess sharp boundaries. Moreover, the ground bundles 

 at least are composite. The several elementary tracts contain fibers 

 passing either from the periphery to the brain along the cord (ascending 

 fibers] or from the brain through the cord to the periphery (descending 

 fibers], or fibers connecting brain and cord or different segments of 

 the cord. For a detailed description of the constitution of these fiber 

 tracts reference must be made to the systematic text-books on the nervous 

 system. 



The larger blood-vessels are distributed along the fibrous septa, 

 taking their origin from the vessels of the pia mater ; the most of them 

 are distributed to the white matter, but to some extent they also supply 

 the gray matter. ' 



The entire surface of the spinal cord presents, just beneath the pia 

 mater, a thin superficial layer or marginal veil of glia tissue. In the 

 brain this layer is somewhat exaggerated in thickness. 



THE REGIONS OF THE SPINAL CORD 



The varying number of fibers which are given off at different levels 

 of the spinal cord results in considerable differences in size in its sev- 

 eral portions. By means of these peculiarities, as well as by the spinal 



