A. J. MACDONALD AND T. S.
KRISHNAN
307
of their internal quality. At weekly intervals
similar sets, each of 12 eggs, were removed from
each group for internal quality determination.
Though candling is still the only practical method
of determining egg quality in unbroken eggs,
this method of judgment is somewhat empirical
and not very suitable for scientific investigations.
In this investigation, the internal quality was
measured by determining (a) the albumen index,
(b) the yolk index, (c) the percentage of thick
white, and (d) the depth of the air cell.
The albumen index is the name given to the
ratio of the height to the mean diameter of
the firm albumen layer. When a high quality
egg is broken out on to a smooth flat surface,
the yolk is found to be in the centre of a compact
layer of thick, jelly-like albumen. The firm al-
bumen layer will have minimum area and maxi-
mum height, with a sharp, smooth and oval
outline. When the quality deteriorates, the
thick white layer begins to flatten out losing
height and increasing in area, till it ruptures
and finally disappears due to complete lique-
faction. Hence, the albumen index decreases
with deterioration in quality. In very good
quality eggs, the index is about 0.1. When
the index figure drops to about 0.03, the thick
albumen layer usually ruptures, when it is no
longer possible to measure the albumen index.
The albumen index figures were obtained by
a slightly modified form of the method used by
Heiman and Carver [1936]. The contents of
the egg were gently broken out on to a smooth,
flat glass plate and measurements made at the
end of two minutes. The height of the firm
albumen was measured by means of a sphero-
meter. Although in the original method, this
height was measured at only one point, it was con-
sidered more accurate to take the average of
three readings made at representative points on
the flat surface of the thick white layer. For
the determination of the mean diameter, the
long axis of the thick white was measured with
sliding calipers. At right angles to it and at
the widest point, a second measurement was
made. The average of these two figures gave
the mean diameter (Plate XXI).
The measurement of yolk index and of air
cell depth were made according to the procedure
outlined by Krishnan [1943]. The percentage
thick white was estimated by the sieve method
of Holst and Almquist [1931] as described by
Macdonald and Krishnan [1942].
EXPERIMENTAL RESULTS
Temperature and humidity
Table I gives the average fortnightly figures
of the temperatures and the relative humidity
in the winter test, and the corresponding weekly
figures for the summer test.
During the first half of the winter test, the
temperature was fairly low and the humidity
comparatively high, both conditions being con-
ducive to the maintenance of good egg quality.
After about the middle of March, i.e., in the
second half of the experimental period, the
temperature rose considerably and the relative
humidity fell to comparatively low levels, thus
contributing to a rapid decline in egg quality.
TABLE I
Record of average temperature and relative humidity
in the egg storage room during the experi-
mental periods
Winter test
Period
(fort-
night
ending)
26-12-40
9-1-41
23-1-41
6-2-41
20-2-41
6-3-41
20-3-41
3-4-41
17-4-41
1-5-41
Average
Tempera-
ture
ºF.
64.0
60.8
61.8
62.6
66.6
71.9
76.0
83.7
89.1
94.8
Average
relative
humidity
per cent
65
72
73
73
74
69
58
45
39
35
Summer test
Period
(week
ending)
27-5-41
3-6-41
10-6-41
18-6-41
25-6-41
2-7-41
9-7-41
17-7-41
24-7-41
31-7-41
7-8-41
Average
Tempera-
ture
ºF.
96.4
98.4
88.2
84.0
96.4
95.1
97.4
97.5
94.9
97.9
91.0
Average
relative
humidity
per cent
30
20
72
72
55
63
67
67
60
58
74
Throughout nearly the whole course of the sum-
mer test, from about the end of May to the end
of July, the average temperatures were com-
paratively steady, ranging from 84.0ºF. to 98.4ºF.
Due to monsoon showers the temperatures
were lower during the third, fourth and tenth
weeks of the experiment. The average relative
humidity was low in the first two weeks but
remained at fairly high levels (55 per cent or
above) during the remainder of the experiment.
EFFECT OF FERTILITY
During the winter test no differences in be-
haviour were observed between fertile and infertile
eggs in any of the groups under test. This is
due to the fact that the average temperature
in the storage room during the first ten weeks
was only about 63ºF. It is, therefore, evident that
fertility doe s not appreciably affect the keeping
quality of eggs, if the storage temperature is
below the critical temperature for embryo develop-
ment. Though the temperature in the storage
room rose above this point and went up to 94.8ºF.
in the second half of the experiment, no visible
interference due to fertility was observed. This
was probably due to the fact that the embryos
in all the fertile eggs kept in storage had died
within the first ten weeks, so that they behaved