-Oct. 15,1924 Postnatal Growth of the Single-Comb White Leghorn 
381 
abundant in this part of the intestine 
is not easy to say. The presence of 
grit in the posterior part of the intestine 
was not observed in the younger chicks. 
Fine sand was found in quantity in the 
gizzard of the one-day-old chick, or 
before there was any food present. 
Jackson and Lowrey (9) find that the 
intestinal contents for the albino rat 
during postnatal life do not average 
more than 5 per cent of the body, 
excepting at 6 weeks, when the average 
was about 8 per cent. 
Yolk sac. —As is well known, the 
yolk sac is inclosed by the abdominal 
wall just before hatching, and the 
resulting scar can readily be seen on the 
young chick just after hatching. Aris¬ 
totle long ago observed the yolk sac 10 
days after hatching; and William 
Harvey found it in a chick 13 days old. 
H. Virchow {27) found the yolk sac 
weighing an average of 5.34 gm. just 
nfter hatching, but reduced to about 
Table I .—Data for the oldest six cases 
in which the yolk sac ivas found 
Sex 
Age in 
! Gross 
j body 
| weight 
Yolk sac 
Percent¬ 
age of 
days 
weight 
_j 
net body 
weight 
Gm. 
• Gm. 
Male_ 
151 : 
1, 633. 2 
0.079 
0. 0050 
Fein ale_ 
167 
1, 324. 7 
.058 
.0046 
Male_ 
172 1 
1, 820. 9 
. 822 j 
.0480 
Female_ 
181 
1, 363. 8 
C) 
( a ) 
Do_ 
202 ! 
1,707.3 
.033 | 
.0020 
Male_ 
237 | 
2, 023. 5 
.858 | 
.0459 
a Yolk sac was 2 mm. in diameter, but was not 
weighed. 
The yolk sac was found in one of two 
conditions. Either it was soft in con¬ 
sistency and more or less imbedded in 
the abdominal wall (as was the last 
one), or it seemed to have broken free 
from its attachments and formed a 
hard spherical structure, filled with a 
more or less chalky mass, in various 
’Fig. 16.—Weight of the esophagus, crop, and intestines (all without contents) plotted on gross body 
weight as the heavier line. Percentage weights plotted as the lighter line 
0.05 gm. on the sixth day. Kaupp ( 11) 
reported an average weight of 8.5 gm. 
for the yolk sac in 10 newly hatched, 
single-comb White Leghorn chicks. 
At 43 hours he found it reduced to 5 
gm., and still present at 120 hours, 
although the weight is not given. 
The findings concerning postnatal 
persistence of the yolk sac are as fol¬ 
lows in the present series: The yolk sac 
was found in every chick, with one 
exception (thirty-first day), up to and 
including the thirty-sixth day. From 
38 to 108 days, inclusive, it was present 
15 times and not found in 12 chicks. 
After the age of 108 days, the yolk sac 
was found in 8 chickens (4 males, 4 
females), the older being a cockerel 237 
days old. It was exceedingly variable 
in weight. For example, the first yolk 
sac weighed 5.05 gm.; at one day, 7.56 
gm. (the heaviest found). In the chick 
at 2 days it weighed but 1.4 gm. and 
at 12 days, 6.01 gm. 
positions in the abdominal cavity and 
with very slight or no attachments. 
Meckel’s diverticulum, or the primi¬ 
tive attachment of the yolk stalk, per¬ 
sists constantly as a small tubular 
outgrowth from the free side of the 
intestine. It was 6 mm. in length in the 
230-day chick, which was about the 
average. There seems to be a tendency 
for this to shorten very slightly with age, 
but even in the hens 2 years old it was 
present as a small diverticulum seyeral 
millimeters in length and always with a 
lumen open widely into the intestine. 
Liver. —The growth in weight of the 
liver and gall bladder (fig. 17) follows 
the same general type of growth curve 
as the other parts of the digestive tract. 
There is no significant sex difference. 
The formulas are: 
y =X o.44 +0 . 017X-5. 29 
from 70-1,500 gm. gross body weight, 
F=0. 00715 (X-l, 500)4-45. 18 
