12 
BULLETIN 565, U. S. DEPARTMENT OF AGRICULTURE. 
take form it appears black on candling. (See PL IX.) An egg con- 
taining a large embryo can not be distinguished from a black rot, 
except by the absence of motion of the contents when the egg is 
turned during candling. Practically all incubated fertile eggs found 
in the candling of eggs for market contain dead embryos. 
After the embryo has died the contents of the egg are subject to 
all the changes making for deterioration which have been described 
for the white and yolk. For example, a yolk bearing a blood ring 
may adhere to the shell or disintegrate and mix with the white. The 
yolk of a partially hatched egg usually attaches itself to the shell by 
the hatch spot or blood ring. 
CLASSIFIED DESCRIPTION OF EGGS BEFORE THE CANDLE AND 
OUT OF THE SHELL. 
The different types of eggs found in commerce may be classified 
according to edibility and possibility of detection by candling as 
follows : 
Table 1. — Eggs classified according to edibility and possibility of detection by 
candling. 
EGGS THAT CAN BE DETECTED BY CANDLING. 
Edible. 
Inedible. 
Illus- 
Illus- 
Kind. 
trated in 
Kind. 
trated in 
Plate No. 
Plate No. 
Fresh egg. 
I, II 
Black rot. 
IV 
Hatch-spot egg. 
III 
Egg with seeping volk. 
Stale egg. 
Mixed rot. 
VI 
Weak egg. 
White rot. 
VII 
Egg with movable air cell.' 
IV 
Blood ring. 
VIII 
Egg with double volk. 1 
Egg with large embrvo. 
IX 
Egg with olive-colored yolk.i 
V 
Egg with bloodv white. 
X 
Egg with slightly stuck yolk. 
Egg with heaviiv stuck volk. 
XI 
Moldv egg. 
IV, XII 
Egg with crusted volk. 
Egg containing blood spots 
or other foreign bodies. 2 
Egg with heaviiv mottled 
yolk. 
i Edible if there is no deterioration. 2 Sometimes edible on removal of body. 
EGGS THAT CAN NOT BE DETECTED BY CANDLING. 
Inedible. 
Kind. 
Egg with green white. 
Musty ogg. 
Sour egg. 
A brief description of the appearance of each type of egg before 
the candle and out of the shell is given in the following pages. The 
principal distinguishing characteristics also are given. These tabu- 
lated descriptions, in conjunction with the table and the illustrations, 
