336 NERVOUS SYSTEM. 
Each half is subdivided by the anterior and posterior lateral 
sulci. 
The posterior lateral sulcus (Fig. 
133, 7; Fig. 134, 4) 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’? (7). 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 
Fic, 133.—Cranrax Portion funiculi (or columns) by the fissures 
OF THE SPINAL CoRD, WITH and sulci, so that there is in each half 
THE CERVICAL ENLARGE. . : 
MENT. DorsaL View. of the cord an anterior, a posterior, 
1-8, the eight cervical and a lateral white funiculus. 
nerves. /-//, first two thoracic 
nerves. 4, dorsal roots (ventral In the cervical region (Fig. 134) 
See seve ie ice. there appears between the posterior 
tral rami; , posterior median lateral and posterior median sulci an 
sulcus; /, posterior lateral sulcus. intermediate sulcus which divides the 
posterior funiculus in this region into two. The median 
slenderer of these is the fasciculus gracilis (7) or column of 
