front matter 1

Sp

in

oc

ep

h

al

ic

tr

ac

ts

Sp

in

oc

ep

h

al

ic

tr

ac

ts

VVentral funiculusentral funiculus

VVentral grayentral gray

Intermediate grayIntermediate gray

Lateral

funiculus

Lateral

funiculus

Vestibulospinal tract?

Dorsal grayDorsal gray

Dorsal root

Dorsal root

bifurcation zone

Fasciculus gracilis

Dorsal root collateralization zone

Lissauer's tract

Dorsal funiculus

Myelinated axons

of ventral horn

motoneurons

Myelinated axons

of ventral horn

motoneurons

Central canal

surrounded by ependyma

Central canal

surrounded by ependyma

Lateral

corticospinal

tract

Lateral

corticospinal

tract

Myelinated terminals of

dorsal root collaterals

Intraspin

al

tr

ac

ts

Intraspin

al

tr

ac

ts

Subgelatinosal pleSubgelatinosal plexusxus

Reticulated areaReticulated area

Ventral white

commissure

Ventral white

commissure

VVentral gray commissureentral gray commissure

Dorsal median septum

Ventral

median fissure

Lateral

reticulospinal

tract?

Lateral

reticulospinal

tract?

Rubrospinal tract?Rubrospinal tract?

See the matched cell body stained section in Plates 102A and B

The ventral commissure stains darkly in this section indicating that all axons in the commissure are myelinated. Fibers in the spino-

cephalic tracts are even more darkly stained than those in Plate 100, indicating myelination is more advanced at this level. The axons

in the spinocephalic tracts at this level are more proximal to their cell bodies of origin than at rostral levels; hence, myelination follows

a proximal (fi rst) to distal (second) gradient.

PLATE 101B