front matter 1

Sp

in

o

ce

p

h

al

ic

t

ra

c

t

s

Sp

in

o

ce

p

h

al

ic

t

ra

c

t

s

VVentral funiculusentral funiculus

Ventral

gray

Ventral

gray

Intermediate

gray

Intermediate

gray

Lateral

funiculus

Lateral

funiculus

Vestibulospinal tract?

Ventral median fissure

Dorsal

gray

Dorsal

Lateral gray

corticospinal
tract

Myelinated terminals of

dorsal root collaterals

Dorsal median septum

Dorsal funiculus

Dorsal root

bifurcation zone

Fasciculus gracilis

Dorsal root

collateralization zone

Lissauer's

tract

VVentral gray commissureentral gray commissure

VVentral white commissureentral white commissure

Myelinated axons from

dorsal root afferents,

intraspinal tract afferents,

and ventral motoneuron efferents

Central canal

surrounded by ependyma

Central canal

surrounded by ependyma

Dorsal

root

Dorsal

root

I

n

tr

aspinal t

ra

ct

I s

n

tr

aspinal t

ra

ct

s

Subgelatinosal pleSubgelatinosal plexusxus

Reticulated areaReticulated area

Lateral

reticulospinal

tract?

Lateral

reticulospinal

tract?

See the matched cell body stained section in Plates 117A and B

The axons in the lateral corticospinal tract at this caudal level are unmy-

elinated. These fi bers are more distal to their cells of origin than they are

at cervical and thoracic levels where they are myelinating (Plates 104,

106, and 108 ). The lateral corticospinal tract is small at this level because

most of the axons have terminated at more rostral levels.

In contrast to the upper cervical level (Plate 104), the axons in the spinocephalic

tracts at this level are more proximal to their cells of origin and are completely

myelinated. Like the lateral corticospinal tract, the spinocephalic tract is smaller at

this level because additional axons join the tract at more rostral levels.

PLATE 116B