388 
Journal of Agricultural Research 
Vol. XXIX, No. 8 
The suprarenals are considerably 
larger in the female rat. Unlike the 
rat, the chicken shows no apparent 
sex difference. 
Hypophysis. —The hypophysis of the 
chicken seems to be quite variable in 
weight, as shown in Figure 25. The 
formulas are: 
F = 0.001(Z°- 34 -0.001Z-1.49) 
from 100-1,600 gm. gross body weight, 
7=0.0000063 (Z—1600) + 0.00919 
from 1,600-2,600 gm. gross body 
weight. 
7 represents the weight of the hy¬ 
pophysis in grams and Z, the gross 
body weight in grams. 
no appreciable sex difference when the 
weights are plotted against body 
weight. If there is any difference at 
all it is rather in favor of a heavier 
male hypophysis. 
UROGENITAL SYSTEM 
Kidneys. —The growth of the kid¬ 
neys plotted against gross body weight 
(fig. 26) shows a marked initial rise 
followed by a gradual decrease in rate 
of growth. The formula is: 
7 = (0.1Z) 0 * 6 —0.0041Z —2.17 
from 100-2,600 gm. gross body weight. 
Y represents the weight of the kid¬ 
neys in grams and Z represents the 
gross body weight in grams. 
Fig. 24.—Relative and absolute weights of the suprarenal glands, plotted against gross body weight. 
There is no apparent sex difference 
A similar irregularity in the arrange¬ 
ment of the cases is observed when age 
rather than gross body weight is used 
for the, abscissae. The percentage 
weights are also variable at first (pos¬ 
sibly because of difficulty in removal). 
After this first irregular period with 
an average of about 0.078 per cent of 
the net body weight, there is a rather 
precipitous fall in the percentage 
weights to about 0.0015 per cent fol¬ 
lowed by a slow decrease to about 
0.0006 per cent, which is also the 
average percentage weight for the three 
older cockerels. The hypophyses of 
the three hens average about 0.0005 
per cent. 
In the rat there is a marked sex 
difference in the weight of the hypo¬ 
physis, the female being the heavier 
according to Hatai (5) and Donald¬ 
son (8). The data on the chick show 
No significant sex difference nor 
peculiarities in the weight of the kid¬ 
neys appear in the older cockerels and 
pullets. 
The percentage weights show a 
marked initial rise followed by the 
usual decrease, and a terminal irreg¬ 
ular portion. At hatching the kid¬ 
neys form 0.6 per cent of the body 
weight, but they rise rapidly until at 
5 days they form 2 per cent, which is 
the highest case of the entire series. 
The average for the older birds would 
be about 0.7 per cent, with the adult 
cases a little less. The older pullets 
seem to have slightly heavier kidneys, 
relative to body weight, than do the 
cockerels of the same age. 
Welcker and Brandt {28) give 0.59 
per cent for the kidneys in two adult 
male chickens, which is about the same 
as the average percentage values for 
