front matter 1

Floor plateFloor plate

Central

canal

Indistinct clusters

of ventral horn

motoneurons?

Indistinct clusters

of ventral horn

motoneurons?

Ventral horn

interneurons

Ventral horn

interneurons

Intermediate

interneurons

Intermediate

interneurons

Dorsal

root

Dorsal

root

Dorsal root

bifurcation zone

Fasciculus cuneatus

(beginning)

Fasciculus gracilis?

Dorsal root

collateralization zone

Lissauer's

tract?

Dorsal funiculus

Dorsal

horn Substantia

gelatinosa

Substantia

gelatinosa

EpendymaEpendyma

Central

autonomic

area

Central

autonomic

area

Lateral horn

motoneurons

Lamina ILamina I

Laminae

IV-V

Laminae

IV-V

Dorsal neuroepithelium

Postulated sojourn zone
of premigratory neurons
in the dorsal neuroepithelium

Lateral

cervical

nucleus

Dorsal

canal

Dorsal

canal

axial

motoneurons

axial

motoneurons

digit

motoneurons

digit

motoneurons

Retreating roof plate

Ventral

white

commissure

Ventral

white

commissure

Ventral

median fissure

Ventral gray

commissure

Ventral gray

commissure

Dorsal median septum

Dorsal intermediate septum

V

e

n

t

r

a

l

fu

nicu

lu

s

V

e

n

t

r

a

l

fu

nicu

lu

s

L a t e r a l f u n i c u l u s

L a t e r a l f u n i c u l u s

Segregating ventral horn

motoneuron columns

Segregating ventral horn

motoneuron columns

PLATE 16B