458 HALBERT L. DUNN 
to present at a later time an outline of the prenatal growth of the 
various internal parts of the brain for which data are now being 
collected. 
Growth of the central nervous system as a whole 
The growth curve of the central nervous system (represented by 
the volume of the central nervous system, fig. 2) is analogous 
in both its character and its slope to the growth curves of nearly 
all the fetal viscera. - The abscissa of this curve is the crown- 
TABLE 35 
Spinal cord volume and weight 
(data of Jackson, ’09, and of Volpin, ’02) 
SPINAL-CORD VOLUME (JACKSON, ’09) SPINAL-CORD WEIGHT (VOLPIN, ’02) 
RANGE OF 
CROWN-HEEL 5 Be, | 
mmrans| | crowo-teel [gg Asatte g| Naber | crowncnect | ,Averaee, | umber 
cm. cm. cc. cm. grams 
Oto 5 sre 0.02225 3 
5 to 10 CRC 0.115 3 
10 to 15 1253 0.1671 3 
15 to 20 hfs 1h 0.3447 5 16.0 0.75 1 
20 to 25 22.4 0. 664 4 20.0 La | 1 
25 to 30 27.4 0.908 5 28.0 2.0 1 
30 to 35 ooaT 1.53 2 32.7 3.0 3 
35 to 40 38.5 1.8 1 38.5 3.75 2 
40 to 45 44,2 3.3 il 41.8 4.5 3 
45 to 50 45.7 6.6 3 
50 to 55 51.9 3.04 2 51.0 9.5 3 
heel length and represents a simple lineal type of growth. The 
value of the central nervous system is therefore a function of the 
crown-heel length which has been raised to approximately the third 
power. Obviously, this is a typical concave volumetric curve. It 
is similar in type to all of the visceral volumetric and ponderal 
curves of growth which have been worked out in this laboratory 
and of which a summary has been published elsewhere (Scammon, 
21). It is also analogous to the curves of fetal body weight 
and of weights of body parts which have been expressed in func- 
tions of the crown-heel length of the fetus. In order to compare 
