228 Cc. M. JACKSON 
VOLUMES OF SUPRARENAL CORTEX AND MEDULLA 
Volumetric data for the relative volumes of the suprarenal cor- 
tex and medulla are given in table 2. These will be considered 
successively, 1) during normal postnatal development; 2) in 
young rats stunted by underfeeding; 3) in such rats refed after 
stunting, and 4) in adult rats subjected to acute or chronic 
inanition.- 
1. During normal postnatal development 
The data summarized in table 2 A include the relative volumes 
of cortex and medulla in groups at various ages, beginning at 
seven days. (In the new-born the cortex and medulla are still 
intermingled and were not measured.) If the data for the abso- 
lute volumes (not given in the table) are considered, it appears 
that both cortex and medulla continue to grow from birth to one 
year of age. Although there are marked individual variations, 
it is on the whole clearly evident that the cortex and medulla 
grow at different rates, so that their relative sizes change. Dur- 
ing the second and third weeks, the cortex grows more rapidly, 
increasing from 75 or 80 per cent to about 90 per cent of the en- 
tire gland, by volume. It apparently continues to increase rela- 
tively, averaging about 93 per cent at ten weeks of age. In 
older rats, there are marked individual variations, but the cortex - 
appears to decrease slightly to 90 or 91 per cent in average relative 
volume. 
The medulla increases more slowly in absolute size, so that its 
relative volume decreases (inversely with the cortex). The me- 
dulla is relatively small in the new-born, though difficult to meas- 
ure on account of the intermingled cortex. In connection with 
the process of confluence, the medulla expands rapidly, being 
relatively largest at one week, forming 20 to 25 per cent of the 
total volume. It decreases to about 15 per cent at two weeks, 10 
per cent at three weeks, and to about 7 per cent at ten weeks, in- 
creasing again slightly to an average of 9 or 10 per cent of the 
entire suprarenal in the older rats. In a few cases in which the 
whole suprarenal gland is relatively small, the medulla was found 
