front matter 1

Floor plateFloor plate

Dorsal

canal

Dorsal

canal

Central

canal

Ventral

canal

Segregating

ventral horn

motoneuron

columns

Segregating

ventral horn

motoneuron

columns

Settling

ventral horn

interneurons

Settling

ventral horn

interneurons

Intermediate

neuroepithelium

Intermediate

neuroepithelium

Receding ventral

neuroepithelium

(source of glia?)

Receding ventral

neuroepithelium

(source of glia?)

Dorsal

neuroepithelium

Dorsal

neuroepithelium

Intermediate

interneurons

Intermediate

interneurons

Roof plate

Cellular roof plate

Fibrous roof plate

Expanding gray matter Floor plate

Expanding white matter

Dorsal root ganglion

Dorsal root

Dorsal root

Ventral root

Spinal nerve

Lateral plate (neuro-

epithelium with NEP cells)

Sojourn zone

of premigratory

neurons destined

for the dorsal horn

and intermediate gray

Sojourn zone

of premigratory

neurons destined

for the dorsal horn

and intermediate gray

Spinal canal with stable dorsal

part and receding ventral part

Migrating and

settling dorsal

horn neurons

Migrating and

settling dorsal

horn neurons

Dorsal root

bifurcation zone

Dorsal root

collateralization zone

Dorsal funiculus

Lateral cervical

nucleus?

Lateral cervical

nucleus?

axial

motoneurons

axial

motoneurons

Sulcus

limitans

Sulcus

limitans

Ventral

white commissure

Ventral

white commissure

V

e

nt

ral fun

ic

ul

u

s

V

e

nt

ral fun

ic

ul

u

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

Incipient

ventral median

fissure

proximal upper

limb motoneurons

proximal upper

limb motoneurons

distal

upper limb

motoneurons

distal

upper limb

motoneurons

Large arrows extending from the neuroepithelium indicate migrating neurons.
Small arrow in the spinal canal indicates the direction of contraction.

PLATE 11B