THE SPINAL CORD.— GENERAL. 



463 



Fia. 327. — General view of spinal cord (Cliauveau). A, cervical bulb; B, lumbar bulb; 

 C, Cauda equina. 



Fig. 828.— Segment of spinal cord at the cervical bulb, or brachial plexus, showing its 

 upper face and the roots of the spinal nerves (Chauveau). A, superior roots; B, 

 inferior roots; C, multiple ganglia of superior roots; D, single ganglion on an 

 exceptional pair; E, £, upper roots passing through the envelopes. 



reception and generation of impulses independent of the brain; 

 or as a conductor of afferent and efferent impulses destined for 

 the brain or originating in that organ. As a matter of fact, 

 however, it is better to bear in mind that the cord and brain 

 constitute one organ or chain of organs, which, as we have 

 learned from our studies in development, are differentiations 

 of one common track, originating from the epiblast. 



While the brain and the cord may act independently to a 



Fig. 329.— Transverse section of spinal cord of child six months old, at middle of lum- 

 bar region, showing especially the fibers of gray substance, 1 x 20. (After Ger- 

 lach.) o, anterior columns; d, posterior columns; c, lateral columns; d, anterior 

 roots; i", posterior roots; /. anterior \vhite commissure- g, central canal lined by 

 epithelial cells; A, connective-tissue substance surrounding it; i, transverse fibers 

 of gray commissure in front, and k, the same behind central canal; I, two veins 

 cut across; m, anterior cornua; n, great lateral cell group of anterior corniia; o, 

 lesser anterior cell group (column); p^ smallest median cell group; q, posterior 

 cornua; n ascending fasciculi in posterior cornua; s, substantia gelatinosa. 



