336 



ANATOMY IN A NUTSHELL. 



the anterior white commissure. It has in it a pro cess of pia mater which conducts 

 blood to the cord. Although there are only eight columns in the whole cord, 

 there are ten tracts in the white matter of each lateral half of the cord. As a 

 rule the tracts are much smaller than the columns, but sometimes they are 

 equal, as in Goll and Burdack. Tracts one, two, three, four, and five are ascend- 



PLATE CLVI. 



Showing the Blood Supply to the Small Intestine. 



ing tracts; eight, nine, and ten are descending tracts, and six and seven are 

 association tracts. (Plate IV). The gray matter in the cord is in the form of 

 a capital letter "H;" the horizontal portion is called the gray commissure, and 

 the portion in front of the central canal is the anterior gray commissure, and 

 the portion behind it the posterior gray commissure. The portion of white 

 matter in front of the gray commissure is the white commissure. The blood 

 supply of the spinal cord and its membranes is (1) from the lateral spinal, which 

 are branches from the subclavian, from thoracic intercostals of the aorta, from 



