448 HALBERT L. DUNN 
The absolute volume of the midbrain when plotted against 
body length (fig. 17) presents a shallow curve and has the em- 
pirical formula: 
Volume of midbrain (cc.) = 0.01 [(0.168 C H 
length (em.))?-5§+12.0] 
TABLE 27 
Volume of the midbrain 
Formula: Midbrain volume (cc.) = .01 [ (.168 crown-heel length (cm.))?*5§ + 12] 
(109 cases) 
Se ee ety ce See CALCULATED peta 
BPE Se) Foe Lee ee B VOLUME OBSERVED AND ones 
Mane ME OF MIDBRAIN CALCULATED 
Range Mean aes Area Mean MEANS 
cm. cm. ce. ce. cc. ce. cc. 
Oto 5 
5 to 10 
10 to 15 12.9 0.3 0.1 0.2 0:2 0 9 
15 to 20 16.9 0.4 0.2 0.3 0.3 0 14 
20 to 25 22.0 0.8 0.3 0.5 0.4 —0.1 lg 
25 to 30 27.0 0.9 0.4 0.6 0.6 0 13 
80 to 35 ByA5 6 1.4 0.4 0.8 0.9 +0.1 16 
35 to 40 Sino lente 0.8 1.4 1.2 —0.2 14 
40 to 45 42.3 2.2 f2 16 1.6 0 il 
45 to 50 48.0 3. 1 125 2.4 2.2 —0.2 Ui 
50 to 55 5222 3.0 1.8 2.4 Papi +0.3 8 
TABLE 28 
Calculated midbrain volume at 5-cm. intervals of crown-heel length 
INCREMENT IN EACH 
CROWN-HEEL LENGTH MIDBRAIN VOLUME Boe eR RATIO TO NEW-BORN 
cm. ce. ce. per cent per cent 
5 
10 0.16 6.6 
15 0.23 0.07 43.7 9.4 
20 0.34 0.11 47.8 13.9 
25 0.51 0.17 50.0 20.9 
30 0.75 0.24 47.0 30.7 
35 1.05 0.30 40.0 43.0 
40 1.48 0.38 36.2 58.5 
45 1.89 0.46 32.0 77.4 
50 2.44 0.55 29.1 100.0 
55 3.12 0.68 27.8 128.0 
