Milford chronicle., 1911-05-05
THE SUCCESSIVE STAGES
Of INCUBATION.
Quoted from Progressive Poultry
Culture" A Brigham, Author.


Selected white-shelled eggs are
placed some under broody hens
and some in an incubator, if one is
available. so as to compare eggs nat
urally and artiicially incubated,
while studying the successive stages
of the development of the embryo
chicks in the egg.
At the end of twenty-four hours
of incubation a change can be de-
teeted in the fertile egg held before
the egg tester, if its search-lght is
very strong and the shell of the egg
thin and white or nearly transparent
By cell division and multiplication
the germs surface or skin (blasto-
derm) has increased in size and
SHOWS against the faint yOlk-shadow
as a small shadow-circle (about one
half inch in diameter), having a
slightly reddish or rosy tint.
At the end of another day the
circle has increased in size to three
fOurths of an inch or perhaps an inch
in diameter and the tint is of slightly
deeper tinge.
After seventy-two hours of incu-
batting the blastoderm shows a de-
cidely bright reddish color especially
if the shell of the egg is nearly trans
parent. Its size has increased to
about one and one-quarter inches.
The central portion appears slightly
lighter than the parts at and near
the circumference.
By holding an egg, during the
early stages of incubation, in a hor-
izontal position against the egg-hole
OF the tester and looking down upon
it as it is gently revolved in the hand
the yOlk is seen to float with the
blastoderm always on its uppermost
side.
By placing two or three fresh eggs
under the setting hen or in the in
eubator on the second day and sew
eral more on the third day, after be-
ginning the experiment, the student
may have at one time, eggs of two
and three days incubating to exam
inc. After comparing these before
the search-light of the egg-tester he
may open their shells and carefully
deposit their contents in separate
saucers or in glass bowls half filled
with water. The beginnings of en-
bryOnic development are plainly |
visible. The blastOderm of the germ
appears on the upper side of the
floating yolk and its color is seen to
be due to the blood, which fills the
fine network or veins spreading out
from the center of the embryo over
the surface of the yOlk. The cir
cumference of the collection of rami-
fying blood vessels is bordered by
vein, which is named the sinus ter
minalis." As the net work of capill-
ary veins enlarges from day to day,
this terminating or bordering vein
extends in a wider circumference,
more and more distant from the EN-
bryo center.
At the end of the fourth day the
outer bordering portion Of the net
work having followed further around
the yolk shows decidedly d 'rker than
the central portion, except for the
dark spot which is the shadow of the
embryo itself.
After five days of incubation are
completed the embryonic develop
ment has become very distinct and
decided. The blood vessels have ex-
tended their meshes fully half way
around the yolk and their shadow
gives a dark appearance to the part
Of the egg that they occupy. The
border of the shadow along the mid
die axis of the egg shows darkest as
the egg is held vertically before the
tester.
The body of the embryo shows in
the midst of the shadow as a blurred !
image with a dark spot near one end
which is an eye.
The embryo. at this stage, shows {
some Independent movement when
the egg is held still before the tester. !
It appears to swim in clear space. s
It is, in fact, surrounded by a sac 6
illed with thin transparent fluid (the {
amnion), which is imbedded in the t
yolk and helps to prevent the en- a
Dryo's too near approach to the shell
Turing the first half of the period of '
incubation. t
At this time eggs from under the t
jetting hens should be carefully COM G
lared with some from the incubator b
L the eggs, from both machine and s
sens, appear alike in their develop s
nent, it is safe to conclude that a
he machine is providing conditions
# incubation that are satisfactory. il
f decided differences in appearance b
.re noticed the same should be care. e
ully studied. The eggs under the I,
n r 1 4. 4