10 BULLETIN 565, F. S. DEPARTMENT OF AGRICULTURE. 
as unmarketable, for during shipment it is very likely to become 
unfit for food. These eggs are difficult to grade accurately by can- 
dling. They- are of such inferior quality, however, that in case of 
doubt they should be classed as inedible. 
The yolk sac may so weaken that the yolk seeps or strains through 
into the white. In these eggs the yolk would appear whole before 
the candle, but it would be weak, and the white would have a cloudy, 
yellow color. Out of the shell the yolk will be seen to be flattened 
and sometimes mottled and the white to be streaked with yolk. 
Very close candling is required to detect these eggs, and since they 
are border-line eggs, in which further deterioration is very rapid, 
they should not be graded as marketable. 1 
The more common form of disintegration of the yolk takes place 
through the rupture in one or more places of the yolk sac and the 
mingling of the white and yolk. This mixing is commonly known 
as " addling." All degrees of addling may be found, from the egg 
in which the yolk is just beginning to mix with the white to the egg 
in which no vestige of white is seen. The eggs representing the 
early stage of mixing are called " mixed rots,'* and those representing 
the later stage, " white rots." Both are inedible. 
Mixed rots are characterized on candling and out of the shell by 
the irregular mixture of white and yolk. Often one portion of the 
yolk shows more deterioration than another, a condition shown by 
a darkened area on candling and by whitish streaks out of the shell. 
(See PL VI.) 
The characteristics noted for mixed rots are even more marked in 
the white rots. In these eggs the white assumes a general yellow 
appearance on candling and out of the shell. (See PL VII.) 
The incrusting of the yolk is a characteristic form of deterioration 
among eggs with soiled shells which have been held in cold storage. 
Under certain conditions the bacteria enter the shell, liquefy the 
white, making it watery, and produce a coating or crust on the yolk. 
Before the candle the yolk appears to have dark, mottled areas. 
Such eggs are unfit for food. 
The position of the yolk also must be taken into consideration when 
grading eggs by candling. In a fresh egg the yolk is slightly above 
the center in the large end of the egg. Although lighter than the 
white, it does not float against the shell because the chalazae tend to 
hold it in a central position in the egg. As the egg becomes stale 
with age, and especially from exposure to heat, the white is weakened, 
thereby making it possible for the yolk to float near the shell. This 
condition indicates staleness if the egg shows shrinkage. 
1 An illustration of an egg with a seeping yolk is published in U. S. Dept. Agr. Bui. 224, 
PI. XVI. 
