SUPRARENAL GLAND—EFFECTS OF INANITION Zhe 
may be compared with the cytomorphosis of the cells of dhe epi- 
dermis, where, however, the process is centroperipheral instead 
of peripherocentral in direction. 
The weight or volume of the suprarenal gland as a whole, to- 
gether with the relative volumes of the cortical and medullary 
constituents, will therefore vary according to the rate of expan- 
sion of the medulla, the rate of erosion of the cortex at the inner 
zone, and the rate of regeneration from the outer zone. Thus 
the postnatal involution of the inner zone in the human suprare- 
nal is so rapid that it is not fully compensated by regeneration 
from the outer zone, or by expansion of the medulla; so the gland 
during the first year actually decreases in weight, as shown by 
the data of Scheel (’08) Starkel and Wegrzynowski (710), and 
others. In the rat the retardarion in the growth of the gland 
during the first week is perhaps explainable upon the same basis. 
Subsequent changes in the absolute and relative volume of the 
cortex in the rat and other forms are evidently subject to much 
variation in different individuals and species. As a rule, how- 
ever, as in the rat, the medulla appears relatively small in vol- 
ume in the earlier prenatal stages (during immigration), expands 
rapidly to a maximum relative size following its confluence (early 
postnatal stages), and thereafter decreases relatively correspond- 
ing to the later more vigorous growth of the cortex (Canalis, ’87; 
Hultgren and Anderson, ’99; Soulié, ’03; Elliott and Tuckett, ’06; 
Scheel, ’08; Starkel and Wegrzynowski, 710; Thomas, ’11, and 
others). 
SUMMARY 
1. In the new-born rat, the suprarenal cortex and medulla are 
not yet distinctly separated, the cortical cell strands in the 
medulla being absorbed during the confluence of the medulla 
in the first, week. During the second and third weeks after 
birth, the cortex increases from 75 or 80 per cent to about 90 per 
cent of the entire gland, by volume. It apparently continues to 
increase relatively to about 93 per cent at ten weeks of age, de- 
creasing slightly in the adult. The medulla increases more 
slowly in absolute volume, thereby decreasing in relative volume 
