A484 HALBERT L. DUNN 
in which Y is the value desired in cc., X is the crown-heel in cm., 
and a, b, and c, are constants determined for the spinal-cord 
volume, the pons and medulla volume, and the midbrain volume. 
Cerebellum growth. Cerebellum growth, as shown by linear 
and volume absolute curves, proceeds slowly until the sixth fetal 
month, and from that time until birth outstrips all other growth 
activities in the central nervous system. 
The lineal determinations expressing this type of growth are 
the vermis cerebelli length and the vermis cerebelli height (fig. 
29, curves III and IV). If plotted against crown-heel length 
and reduced to per cents of their new-born values, they lie close 
together and ascend slowly at first and then more rapidly to birth 
in very shallow concave curves. They are decidedly different 
from all other straight-line absolute curves of the nervous system, 
resembling volumetric curves rather than lineal progressions. 
They show a similar definite classification when calculated against 
fetal months (fig. 33, curves III and IV). The rate of growth 
of the cerebellum, as shown by the percentage increment curves 
of the vermis cerebelli length and the vermis cerebelli height 
either when calculated for 5-em. C H intervals (fig. 25, curves 
III and IV) or for age in fetal months (fig. 27, curves VIII and 
IX), reflect the cerebellum type of growth. During the last four 
fetal months the percentage increment of the vermis cerebelli 
length and the vermis cerebelli height is higher by 8 to 10 per 
cent than all other linear percentage increment curves of the cen- 
tral nervous system. 
A consideration of the vermis cerebelli length and the vermis 
cerebelli height formulae (table 43) shows the volumetric tendency 
of these linear formulae. They can be expressed by the general 
empirical formula: 
Vi = Oi Xe) 
in which Y is the value desired in em., X is crown-heel in cm., 
and a and 6 are constants determined for both the vermis cere- 
belli length and the vermis cerebelli height. 
The curve of the volume of the cerebellum is striking in char- 
acter and demonstrates the slow growth of the structure prior 
