oct. 15,1924 Postnatal Growth of the Single-Comb White Leghorn 
389 
the three older cockerels of the present 
investigation. Jackson (8) gives the 
following percentage weights for the 
kidneys of the male rat: At birth, 0.96 
per cent; at seven days, 1.29 per cent; 
and a maximum of 1.44 per cent at 
twenty days; it then decreases to 0.95 
per cent at one year. 
Ovary and oviduct. —Figure 27 
shows the increase in weight of the 
ovary (large dot) and oviduct (circle) 
plotted against age. The distribution 
of cases is very irregular but less so 
than when plotted against body weight. 
No attempt has been made to draw a 
curve or derive a formula for these 
organs, since both are very irregular in 
their growth and the number of cases 
is not sufficient to justify a curve. The 
tinues to be the heavier, with two 
individual exceptions: The pullet at 
286 days and one of the 2-year-old 
hens. 
The pullet at 18S days had a fully 
developed egg in the lower end of the 
oviduct and the following day an egg 
was laid by one of the other pullets 
of this group (Group 1). Between 
the pullet at 181 days and that at 188 
days, in an interval of seven days, the 
oviduct shows an increase from 8.66 
gm. to 82.75 gm., or about 8.6 times; 
while the ovary has increased from 
2.108 gm. to 38.94 gm. or 17.5 times. 
In addition, the ovary and oviduct 
have produced the egg which was 
found in the oviduct of the pullet at 
188 days. 
Fig. 25*—Absolute and relative weights of the hypophysis, plotted on gross body weight 
-weights are for the empty oviduct. 
One egg (never more) was sometimes 
found in the oviduct, but it was re¬ 
moved before weighing the egg tube. 
Four phases of ovarian growth are 
recognized: (1) an initial period of 
very slow growth, followed by (2) a 
slight increase in growth rate; then (3) 
a* * period of very slow growth followed 
by (4) a second period of more rapid 
growth. There is a brief prepuberal 
period of rapid growth which lasts but 
.about 30 days, or from about 160 to 
190 days of age. 
The oviduct was not weighed in the 
smaller chicks, but from about 80 
'days up to 160 days of age it was 
always a little lighter than the ovary. 
In the pullet at 162 days the positions 
on the chart were reversed, the oviduct 
becoming heavier. The oviduct con- 
Table II .—Growth in diameter of the 
largest ovum in the ovaries of the 
;pullets of Series I 
Chick number 
! Dia- 
: meter 
Age of 
i largest 
I ovum 
i. 
'I 
Days \ Mm. 
1-31_ 162 : 4.5 
1-33_ 167 | 3.0 
1-35_ 174 1 7.0 
1-37_ ! 181 : 9.0 
1-39_ 188 : O) 
* Mature egg in terminal part of oviduct. 
The relative weights of ovary and 
oviduct undergo a correspondingly 
large increase. The oviduct increases 
