POULTRY LABORATORY GUIDE 35 



The circular opening should be about six inches 

 above the waist hne for the best work. Take 

 the untested eggs in the left hand, two or three 

 at a time, transfer them one at a time to the 

 right hand, grasping the eggs between the thumb 

 and two first fingers with the large or air-cell end 

 outwards. Place this large end in the circular 

 opening in the testing box, gently revolve the 

 egg between the fingers, and the strong rays of 

 Ught will penetrate the egg, making its contents 

 visible. This causes the germ, if present, to 

 change its position, making it the more easily 

 distinguished. 



The important facts to be noted in the first 

 test are the following:^ 



Size and location of air cell. 



Infertile eggs. 



Dead germs. 



Germs adhering to the shell.' 



Cracked eggs. 

 I. The size of the air cell varies with the period 

 of incubation and the rapidity with which the 

 Uquids of the egg have evaporated during incu- 

 bation. The more moisture in the air the less 

 evaporation, and consequently the smaller air 

 cell; the drier the air the more evaporation 

 and the larger the air cell. Under normal 

 humid conditions the air cell of a hen's egg 



