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 yolk. 





Stale egg. 





Mixed rot. 



VI 



Weak egg. 





White rot. 



VII 



Egg with movable air cell. 1 



IV 



Blood ring. 



VIII 



Egg with double yolk.i 





Egg with large embryo. 



IX 



Egg with olive-colored yolk.i 



V 



Egg with bloody white. 



X 







Egg with slightly stuck yolk. 



XI 







Egg with heavily stuck yolk. 









Moldy egg. 



IV, XII 







Egg with crusted yolk. 









Egg containing blood spots 









or other foreign bodies.* 









Egg with heavily mottled 









yolk. 





1 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 egg. 

 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, 



