336 



NERVOUS SYSTEM. 



Each half is subdivided by the anterior and posterior lateral 



sulci. 



The posterior lateral sulcus (Fig. 

 !33. /; Fig. T 34> ^) lies at the side of 

 the posterior median sulcus. It is 

 broad and shallow and has the pos- 

 terior roots of the spinal nerves emerg- 

 ing from its bottom. 



The anterior lateral sulcus exists 

 only after the forcible pulling out of 

 the anterior (ventral) roots of the 

 spinal nerves. It then marks the line 

 along which they originate from the 

 cord. 



In cross-section (Fig. 134) the 

 substance of the cord appears to the 

 naked eye as composed of a darker 

 central "gray matter" (g) and of an 

 outer "white matter" (/). The 

 gray matter has in section the form of 

 the letter H. The cord is really 

 tubular, having a central canal (//) 

 which appears in section in the middle 

 of the cross-bar of the H, while the 

 two ends of each vertical bar extend 

 toward the anterior and posterior 

 lateral fissures. 



The white matter is divided into 



FIG. 133. CRANIAL PORTION funiculi (or columns) by the fissures 

 OF THE SPINAL CORD, WITH and suk j go that there j s j n each half 

 THE CERVICAL ENLARGE 



MENT. DORSAL VIEW. of the cord an anterior, a posterior, 

 1-8, the eight cervical anc j a lateral white funiculus. 



nerves. /-//, first two thoracic 



nerves, a, dorsal roots (ventral In the Cervical region (Fig. 134) 



roots not shown); 6, spinal there appears between the posterior 



ganglia ; c , dorsal rami ; a, ven- 

 tral rami; e, posterior median lateral and posterior median sulci an 

 sulcus;/,posteriorlateralsulcus. interme diate sulcus which divides the 



posterior funiculus in this region into two. The median 

 slenderer of these is the fasciculus gracilis (d) or column of 



