GROWTH OF THE FETAL CENTRAL NERVOUS SYSTEM 425 
fetuses of 25 to 30 em. (C H) they have reached an average volume 
After this time the volume curve increases more 
rapidly, attaining the average of about 300 cc. at 50 em. (C H). 
When examined in relation to age (fig. 34, curve II) the ab- 
solute volume of the right cerebral hemisphere is found to be 2 ee. 
of about 32 ce. 
CROWN-HEEL LENGTH 
Range 
cm. 
Oto 5 
5 to 10 
10 to 15 
15 to 20 
20 to 25 
25 to 30 
30 to 35 
35 to 40 
40 to 45 
45 to 50 
50 to 55 
TABLE 9 
Volume of the left cerebral hemisphere 
Formula: Volume of the left cerebral hemisphere (cc.) = (0.105 crown-heel 
length (cm.))*% 
OBSERVED VOLUME OF THE 
LEFT HEMISPHERE 
Maxi- 
Mean mish 
cm. ce. 
12.5 4.4 
16.9} 10.5 
22.4 | 20.0 
Phd | 3020 
32.8 | 50.0 
37.2 | 89.6 
42.5 | 110.7 | 
48.0 | 188.5 | 
52.2 | 192.0 
1.3 
2.3 
10.2 
13.0 
21.0 
46.8 
67.0 
98.5 
142.0 
Mean 
ce. ce 
2.6 2.3 
6.0 sac 
14.8 13.5 
21.7 24.0 
35:2) 429 
64.1 62.9 
92.2 94.4 
138.0 136.6 
170.0 176.2 
TABLE 10 
CALCULATED 
VOLUME OF 
THE LEFT 
HEMISPHERE 
DIFFERENCE 
BETWEEN 
OBSERVED AND 
CALCULATED 
MEANS 
cc. 
—0.3 
—0.3 
—0.3 
+2.3 
+4.7 
ee 
+2.2 
al: 
+6.2 
NUMBER 
OF CASES 
Calculated volume of left cerebral hemisphere at 5-cm. intervals of crown-heel length 
CROWN-HEEL LENGTH 
VOLUME OF LEFT 
CEREBRAL HEMISPHERE 
200.3 
INCREMENT IN EACH 
5-cM. INTERVAL 
cc. 
2.8 
5.6 
9.2 
14.0 
1957 
25.8 
32.9 
43.7 
45 .4 
per cent 
233 .0 
140.0 
96.0 
74.5 
60.0 
49.1 
42.0 
39.2 
29.3 
RATIO TO NEW-BORN 
OF CROWN-HEEL LENGTH 
per cent 
0.8 
2.6 
6.2 
12.1 
21.2 
33.9 
50.6 
