THE CENTRAL NERVOUS SYSTEM. 345 
foramen cecum (g). The dorsal (posterior) sulcus (Fig. 141, 
a) is well marked; it erids at the caudal boundary of the fourth 
ventricle (4). 
The anterior lateral sulcus (Fig. 138, 7) may be traced 
craniad from the origin of the ventral roots of the first cervical 
nerves (s), along the lateral border of the area elliptica (x), 
then curving mediad to the lateral border of the pyramis (0), 
and finally reaching the pons (7). Its position is marked by 
the origin of the roots of the hypoglossal nerve (X//). 
The posterior lateral sulcus (Fig. 141, 4), marked on the 
spinal cord by the origin of the dorsal nerve-roots, curves 
laterad at the sides of the fourth ventricle (4) owing to the 
increasing width of the latter, and ends at an elevated area of 
oblique fibres, the area ovalis (/). 
The columns or funiculi bounded by the longitudinal 
fissures present the following peculiarities: 
The anterior white funiculus of the cord is replaced in the 
medulla by the pyramidal tracts (pyramides) (Fig. 138, 0). 
The pyramidal tracts are formed by fibres which emerge from 
beneath the pons and pass caudad to disappear just craniad of 
the level of the first cervical nerve (s). The pyramidal tracts 
are bounded medially by the anterior median fissure (/), but 
laterally each is separated from the anterior lateral sulcus (7) 
over its caudal part by an elongated area elliptica (x), the 
human homologue of which is uncertain. It perhaps represents 
the oliva. 
Laterad of the cranial portion of the pyramids is an irreg- 
ular area known as the trapezium (/) which abuts caudad on 
the area elliptica (z) and the area ovalis (#). The area ovalis 
(Fig. 138, m; Fig. 141, /) (or zonula Arnoldi) is a broad band 
of oblique fives which passes from the lateral side of the area 
elliptica craniodorsad to disappear under the cerebellum. 
The posterior white funiculus was divided in the cervical 
region into two, the fasciculus gracilis (column of Goll) and 
the fasciculus cuneatus (column of Burdach). The fasciculus 
gracilis (Fig. 141, ¢) extends to the caudal end of the fourth 
ventricle (#) and ends there in an expansion, the clava (2), 
which forms the -posterior boundary of the fourth ventricle. 
