548 



NERVOUS SYSTEM 



PHYSIOLOGICAL ANATOMY OF THE SPINAL CORD 



The spinal cord, with its membranes, the roots of the spinal 

 nerves and the surrounding liquid, occupies the spinal canal and is 

 continuous with the encephalon. Its length is fifteen to eighteen 

 inches (38.1 to 45.7 centimeters) and its weight is about an ounce and 

 a half (42.5 grams). Its general form is cylindrical, but it is slightly 



Fig. 132. Transverse section of the spinal cord of a child six months old, at the middle of the lum- 

 bar enlargement, treated with potassium auric chloride and uranium nitrate ; X 20. By means of 

 these reagents, the direction of the fibres in the gray substance is rendered unusually distinct (Gerlach). 



a, anterior columns ; b, posterior columns ; c, lateral columns ; d, anterior roots ; e, posterior roots ; 

 f, anterior white commissure, in communication with the fasciculi of the anterior cornua and the 

 anterior columns ; g, central canal, with its epithelium ; h, surrounding connective substance of the 

 central canal; i, transverse fasciculi of the gray commissure in front of the central canal; >, transverse 

 fasciculi of the gray commissure behind the central canal ; /, transverse section of the two central 

 veins ; m, anterior cornua ; n, great, lateral cellular layer of the anterior cornua ; o, lesser, anterior 

 cellular layer; p, smallest, median cellular layer; q, posterior cornua; r, ascending fasciculi in the 

 posterior cornua ; s, substantia gelatinosa. 



flattened in certain portions. It extends from the foramen magnum to 

 the lower border of the body of the first lumbar vertebra. It presents, 

 at the origin of the brachial nerves, an elongated ovoid enlargement 

 flattened antero-posteriorly, and a corresponding enlargement at the 

 origin of the nerves that supply the lower extremities. It terminates 

 below in a slender gray filament, called the filum terminale, at the lower 



