front matter 1

G

W

1

0

. 5

.5% .7%

52.7%

.7% .4%

45%

G

W

1

.2% .5% 9

49.8%

.4% .1%

49%

GW

(^26)

58.5% 41.3%

.2%

CENTRAL CANAL

AND EPENDYMA

.2%

CENTRAL CANAL

AND EPENDYMA

GW

(^37)

62.12% 37.75%

.14%

CENTRAL CANAL

AND EPENDYMA

.14%

CENTRAL CANAL

AND EPENDYMA

(^4) T

H

W

E

E

K

27.74%

72.14%

.12%

CENTRAL CANAL

AND EPENDYMA

.12%

CENTRAL CANAL

AND EPENDYMA

FLOOR PLATE

WHITE MATTER CENTRAL CANAL ROOF PLATE

GRAY MATTER EPENDYMA

Proportional Areas at the Cervical Enlargement

Figure 35. A continuation of the previous fi gure in specimens at GW10.5 (see section measured in Plate 23), GW19 (Plate 40), GW26 (Plate 47), GW37
(Plate 65), and the 4th postnatal week (Plate 95). During this period, the proportional areas of the gray and white matter make up most of the spinal cord.
The roof and fl oor plates disappear by GW26, and the proportional areas of the central canal and ependyma are so small that they appear as a slightly
thicker black line separating the gray matter and white matter at the 12:00 position of each pie graph. The gray matter continually loses proportional
area throughout this period but the absolute area does increase gradually as neurons grow dendrites and some interneurons grow elaborate terminal axon
arbors (especially in the dorsal horn). The proportion of the white matter continually increases during this time, and it is the largest proportional area
from GW26 onward.

FIGURE 35