front matter 1

Sp

in

oc

ep

h

al

ic

tr

a

c

ts

?

Sp

in

oc

ep

h

al

ic

tr

a

c

ts

?

VVentral funiculusentral funiculus

VVentral grayentral gray

Intermediate grayIntermediate gray

Lateral

funiculus

Lateral

funiculus

Tectospinal tract?

Medial longitudinal fasciculus?

Vestibulospinal tract?

Dorsal grayDorsal gray

VVentral rootletsentral rootlets

Ventral root

Dorsal root

Ventral corticospinal tract

Lateral

reticulospinal tract?

Lateral

reticulospinal tract?

Fasciculus gracilis

Fasciculus cuneatus

Myelinated

terminals of

dorsal root

collaterals

Myelinated

terminals of

dorsal root

collaterals

Dorsal funiculus

Dorsal root bifurcation zone

Dorsal root collateralization zone

Lissauer's

tract

Lateral corticospinal

tract

Lateral corticospinal

tract

Central canal

surrounded by ependyma

Central canal

surrounded by ependyma

VVentral white commissureentral white commissure

Myelinated axons VVentral gray commissureentral gray commissure

of ventral horn

motoneurons

Myelinated axons

of ventral horn

motoneurons

S

p

in

o c e r e b e l l a r t r a c t s?

S

p

in

o c e r e b e l l a r t r a c t s?

Intr

as

p

in

a

l

t

r

a

c

t

s

?

Intr

as

p

in

a

l

t

r

a

c

t

s

?

Examples of myelination

and concentrations

of reactive glia

Examples of myelination

and concentrations

of reactive glia

Few myelinated fibers

Sparse reactive glia

Many myelinated fibers

Myelinated

Dorsal median septum

Ventral

median fissure

Dorsal intermediate septum

Very sparse

reactive glia

Sparse

reactive glia

Subgelatinosal pleSubgelatinosal plexusxus

Reticulated areaReticulated area

myelinationgradient

myelination

gradient

myelination

gradient

See the matched cell body stained section in Plates 81A 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 medial and central parts of the

intraspinal tracts, and the internal 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 medial longitudinal fasciculus, the tectospinal tract, and the lateral reticulospinal tract.

PLATE 80B