2O2 ANATOMY AND PHYSIOLOGY FOR NURSES 



the spinal canal, extending from the foramen magnum to 

 the lower border of the first lumbar vertebra, where it 

 terminates in slender filaments of gray substance. Its 

 weight, when divested of all its membranes and nerves, is 

 about 1 1 ounces. It is usually about 16 or 17 inches in 

 length. It varies in its diameter at different locations. 



FIG. 104. Different views of a portion of the spinal cord from the cervi- 

 cal region, with the roots of the nerves. In A the anterior surface of the 

 specimen is shown, the anterior nerve-root of its right side being 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 com- 

 pound nerve ; 7', the posterior primary branch seen in A and D to be de- 

 rived in part from the anterior and in part from the posterior root (Allen 

 Thomson). 



It is grooved, on both its anterior and its posterior sur- 

 face, by a furrow that divides it in its entire length into 

 two great nervous cords intimately united with each other. 

 These lateral cords are each divided by furrows into three 

 distinct sets of fibers or columns; namely, the anterior, 

 lateral, and posterior columns. The anterior are the 

 motor columns; the posterior, those of sensation; the 



