HOW TO CANDLE EGOS. 9 



Green- white eggs x are caused by bacteria which have penetrated a 

 damaged or wet shell. These organisms grow in both the white and 

 the yolk, producing in the former a very characteristic green color. 

 Only in exceptional cases is the egg shell sufficiently transparent for 

 the green color of the white to be seen by candling. Eggs with green 

 whites represent one of the few kinds of bad eggs which can not be 

 determined by inspection through the shell. 



Mold may penetrate a wet, broken shell and attach itself to the 

 inner surface in the form of irregular patches. If the growth takes 

 place at low temperatures, the affected portions of the white are gela- 

 tinized. These mold spots appear as dark areas before the candle, 

 and are seen easily if not covered with the fingers. ( See Pis. IV and 

 XII.) 



Foreign bodies, such as meat spots, grain, gravel, or worms, may 

 be included in the egg in its passage down the oviduct. Before the 

 candle they appear as dark spots moving in the white. 



THE YOLK. 



The conditions to be noted when studying the yolk may be divided 

 into two classes, namely, those relating to ordinary decay and those 

 pertaining to changes taking place during hatching. 



CHANGES IN THE YOLK DUE TO DECAY. 



The condition of the yolk is one of the most important factors to be 

 determined when judging the quality of eggs by candling. When a 

 fresh egg is twirled before the candle the yolk is dimly seen as a dark 

 and shadowy object moving slowly in the white. The more trans- 

 parent the shell the more distinctly is the yolk seen. The yolk sac is 

 so strong and the white so firm that the spherical form of the yolk is 

 altered very little when the contents of the egg are set in motion by 

 the turning during candling. 



Because of the thinner condition of the white, the yolk of a stale 

 egg is seen much more plainly on candling than that of a fresh egg. 

 As the egg ages the yolk sac weakens, and since the white becomes 

 thinner at the same time the outline of the yolk is seen to change 

 when the egg is rotated. When such an egg is opened the yolk flat- 

 tens out and often breaks. The differences in the strength of the yolk 

 sac of eggs of varying degrees of freshness are indicated clearly in 

 Plates I and III. If eggs which have weak yolks before the candle 

 show whole yolks when opened, they are graded as good if no other 

 cause for rejection is observed. 



When the yolk of an egg is so weak that a shake in the hand 

 causes it to break and mix with the white, the egg should be graded 



1 Illustrated in color in U. S. Dept. Agr. Bui. 51, PI. VIII. 



