1 10 



THE NERVE TISSUE 



Structure of the Spinal Cord.— The gray matter in the cerel^riim 

 and cerebelhun is external and eo\'ers the white matter. In the 

 spinal cord the o;ray matter is internal and more or less surrounded 

 by white matter. The cord is almost divided into two halves by 

 a deep median dorsal septum and a shallower, wider, median ventral 

 fissure. However, the two halves are connected by a white and 

 gray commissure. The gray matter resembles the letter "X" or 

 letter "H." The narrower dorsal horns of gray matter extend almost 

 to the periphery. (Fig. ()o.) The ventral horns are much wider 



^Dorsal median septum 

 ^^o ^>?T^ c V, ^ or fal column of white matter 

 ^^^— Origin of dorsal root 



Dorsal horn of /i^i ' 

 graij matter f/'^^^^ 



mm 



White matter^fm ^ 'M 





-Lateral column 



Spinal canal pixSi'iV'j 



Doff^ 



Gray matter \i™ — 

 Ventral horn of ^^fc^o ' s) 



gray matter 



fcr^il 



i ^o^E'Kl of white matter 



-Origin of ventral root 



Ventral median fissure^ Ventral column of white matter 

 Fig. 6.S. — Diagram showing regions of the spinal cord. 



and do not extend to the ventro-lateral surface. The dorsal median 

 septum extends down to the gray commissure, and the latter con- 

 tains the canal of the spinal cord which is lined by ependymal cells. 

 Ventral to the gray commissure is a white commissure. The white 

 matter between the dorsal septimi and the gray horn adjacent to it 

 is known as the dorsal funiculus or column of white matter. \'entral 

 and lateral to the dorsal horns on either side is the ventro-lateral 

 column or funiculus. The latter white matter may be subdi\'ided 

 into a ^•entral coliunn betw^een the ventral fissure and the gray 

 matter of the ventral horn adjacent to it. The white matter dorsal 

 and lateral to this is known as the lateral column of each side. The 

 white matter consists of myelinated and unmyelinated axons, 

 and neuroglia but no neurolemma. The surface of the cord is 

 immediately covered with ])ia mater and this extends into the 

 white matter as short septa in places. Studies of \ari()iis kinds 



