THE CENTRAL NERVOUS SYSTEM. 289 



in the middle of which lies the minute central canal, the direct 



Section of spinal cord from lower part of lumbar region of child : V, D, ventral and dorsal 

 median fissures. 



continuation of the ventricular cavities of the encephalon and the 

 remains of the large neural canal of early foetal life. That part of 



FIG. 323. 



Portion of section of spinal cord of calf, including central canal and 

 commissures : a, b, anterior and posterior median fissures ; c, central canal, 

 lined with ciliated epithelium, d ; e, surrounding substantia gelatinosa ; f, 

 gray commissure ; g. white matter ; h, white commissure ; , decussating 

 nerve-fibres ; k, nerve-fibres in section. 



the gray commissure lying in front of the central canal constitutes 



'9 



