THE SPINAL CORD 



237 



ingly vascular; indeed its main function is to support vessels be- 

 longing to the nervous substance underneath. Both the arach- 

 noid and the pia mater pass out at the foramen magnum with 

 the dura to cover the cord. 



The Spinal Cord. 



The spinal cord occupies the spinal canal and is about eight- 

 een inches long, extending from the foramen magnum to the 

 lower border of the first lumbar vertebra. Its distal extremity is 



FIG. 73. Different views of a portion of the spinal cord from the cervical 

 region, with the roots of the nerves. (Slightly enlarged.) 



In A, the anterior surface of the specimen is shown; the anterior nerve -root of its 

 right side is divided; in B, a view of the right side is given; in C, the upper surface is 

 shown; in D, the nerve-roots and ganglion are shown from below, i, the anterior 

 median fissure; 2, posterior median fissure; 3, anterior lateral depression, over which 

 the anterior nerve-roots are seen to spread; 4, posterior lateral groove, into which 

 the posterior roots are seen to sink; 5, anterior roots passing the ganglion; 5', in A, 

 the anterior root divided; 6, the posterior roots, the fibers of which pass into the 

 ganglion 6'; 7, the united or compound nerve; 7', the posterior primary branch, seen 

 in A and D to be derived in part from the anterior and in part from the posterior 

 root. (Kirkes after Allen Thomson.) 



