442 HALBERT L. DUNN 
growth of about 126 per cent for the fourth month, falls to 58 per 
cent for the fifth month, and then descends steadily to about 13 
per cent for the tenth month. 
The growth of the cerebellum during the latter part of fetal 
life is also strikingly illustrated by the midsagittal sections 
shown in figures 37 and 38. In the third fetal month (figure 
38, C) the cerebellum grows posteriorly and parallel to the pons 
and medulla; by the middle of the sixth fetal month (fig. 38, D, E, 
F) it assumes its characteristic shape and position in relation to 
the cerebral hemispheres. From the middle of the sixth fetal 
month to birth (fig. 38, G to I, inclusive) each succeeding tracing 
indicates a greater relative size in this portion of the brain. 
It will be noted in this connection that the graphs of absolute 
growth of the cerebellum in both of the linear dimensions resemble 
volume curves much more closely than does the graphic expression 
of any other lineal dimensions of the nervous system. 
Growth of the pons and medulla 
The growth of the pons and medulla (fig. 14) presents a typical 
volume curve having the empirical formula: 
Pons and medulla vohime (cc.) = 0.01 [(0.2 C H body length 
(em.))2-67 + 20.0] 
At 10 em. (C H) their volume is about 0.3 cc., by 30 em. (C H) 
‘ it is 1.4 ec., and at birth (50 cm. C H) it is approximately 5 cc. 
When calculated for age in fetal months (fig. 35, curve IJ), their 
volume is 0.2 ce. at three months and 1.4 cc. at six months. 
From this time it rises steadily to about 5 ce. at birth. 
The percentage increment of the volume (fig. 26, curve VIII) 
is approximately 50 per cent for the 10-to-15-em. (C H) interval 
and rises to about 56 to 57 per cent for the interval between 15 
to 20 em. It then descends steadily to about 27 per cent from 
50 to 55 em. (C H). 
The percentage increment of the pons and medulla volume as 
calculated for fetal months (fig. 28, curve II) shows a rate of 
growth of about 96 per cent for the fourth month, and then de- 
scends steadily to about 27.5 per cent for the last month of pre- 
natal life. 
