242 Cc. M. JACKSON 
’13), the suprarenal gland in the albino rat increases but slightly 
in average absolute weight (from 0.0019 gram to 0.0023 gram) 
during the first week after birth, thereby decreasing in relative 
weight (percentage of the entire body). This is in agreement 
with the sma ler size of the cortical cells (already mentioned) 
and the corresponding marked decrease in the rate of mitosis 
observed in the present study (table 5). The weight of the 
gland increases rapidly during the second and third weeks, reach 
ing its maximun relative size corresponding to the period when 
an increase in the number of mitoses appears. The formula 
for the growth of the suprarenal in the albino rat as derived 
by Hatai (13) similarly indicates a maximum relative weight 
for suprarenal at about 10 to 15 grams body weight. His data, 
however, do not show the arrested growth during the first week. 
The suprarenal weights in Donaldson’s (715) tables (which are 
based upon Hatai’s formulas) are therefore apparently too high 
for this early period. According to these tables, at a body 
weight of 10 grams, the suprarenals should weigh about 0.0045 
gram, whereas in fifty-seven cases (30 m., 27 f.) I found an aver- 
age of only about 0.0023 gram. 
As to regional distribution, cell division has in general been 
found to occur throughout the gland in the earlier stages, espe- 
cially prenatal (Canalis, ’87, in dog, guinea-pig, and rabbit), 
with a progressive tendency to be restricted later to the outer 
cortical region (Canalis, ’87; Mulon, ’03 b, and others). The 
occurrence of mitosis in the deeper layers of the suprarenal 
cortex (occasionally even in the zona reticularis) in growing 
or adult animals has also been observed by Bonnamour (’05 a), 
Kolmer (’12 b), and Da Costa (’13) (dog, rat, rabbit, guinea-pig). 
An extraordinary increase in mitosis in the outer part of the 
zona fasciculata was noted by Kolmer (12 a) at the end of preg- 
nancy in the guinea-pig. That the outer cortical region of the 
suprarenal is the chief ‘germinative zone’ from which by cell 
division the remainder of the cortex is derived (especially in 
postnatal development), is indicated by the observations of 
Canalis (’87), Roud (’02), Cristiani (’02), Soulié (03), Mulon 
(03 b, 05 a), Kern (11), Kolmer (12b), Cottentot, Mulon 
