front matter 1

Sp

in

oc

ep

h

a

li

c

tr

a

c

ts

?

Sp

in

oc

ep

h

a

li

c

tr

a

c

ts

?

Ventral white commissure

Ventral gray commissure

VVentral funiculusentral funiculus

Ventral corticospinal tract?

Central canal with

surrounding ependyma

VVentral grayentral gray

Intermediate grayIntermediate gray

Dorsal root

bifurcation zone

Superficial fasciculus gracilis

Deep fasciculus gracilis

Dorsal root

collateralization zone

Lissauer's

tract

Lateral funiculusLateral funiculus

Lateral

corticospinal

tract

Lateral

corticospinal

tract

Clarke's

column

Clarke's

column

Vestibulospinal tract?

Dorsal grayDorsal gray

Dorsal funiculus

Myelinating terminals

of dorsal root collaterals

Myelinating terminals

of dorsal root collaterals

Examples of myelination and
concentrations of reactive glia

Many myelinating fibers

Some myelinating fibers

Very sparse reactive glia

Dense reactive glia

An example of sparse reactive glia

Incipient

subgelatinosal

plexus

Incipient

subgelatinosal

plexus

Reticulated

area

Reticulated

area

Lateral

reticulospinal tract?

Lateral

reticulospinal tract?

Rubrospinal tract?Rubrospinal tract?

Dorsal median septum

Ventral median fissure

I

n

t

ra spina

l

t

r

a

c

t

s

?

I

n

t

ra spina

l

t

r

a

c

t

s

?

Sp

in

o c e r e b e l

l

a

r

t

r

a

c

t

s

?

Sp

in

o c e r e b e l

l

a

r

t

r

a

c

t

s

?

See the matched cell body stained section in Plates 55A and B

The fi ne lines in the lateral and ventral funiculi segregate regions of differing densities of the myelin stain, not the borders of fi ber tracts. These

lines may correspond to the borders of some fi ber tracts, such as the spinocerebellar and the lateral corticospinal tracts. Other lines run across

fi ber tracts, such as the area surrounding the ventral horn that includes the central part of the intraspinal tracts, the vestibulospinal tract, and the

ventral and central fi bers of the spinocephalic tracts. Most tracts in the ventral and lateral funiculi overlap and do not have distinct borders. The

ventral part of the spinocephalic tracts overlaps with the vestibulospinal tract; its central part includes fi bers in the ventrolateral reticulospinal

tract (not labeled), the spinotectal tract (not labeled), and the spino-olivary tract (not labeled). The intraspinal tracts overlap with the lateral

reticulospinal tract. Some fi bers of the rubrospinal tract may intermingle with ventral fi bers of the lateral corticospinal tract.

PLATE 54B