POULTRY LABORATORY GUIDE 47 



occupy the whole of the shell except the air space. 

 The yolk will be seen almost entirely absorbed, 

 the walls being loose and flabby. Just previous 

 to hatching the yolk is drawn into the body, the 

 walls closing over it at the umbilicus. This yolk 

 enclosed within the body serves to supply the 

 chick with food for twenty-four to thirty-six hours 

 after hatching. 



Notice the movement of the embryo after the 

 fourteenth day, also the beating of the heart, 

 which will continue for, a long time after the 

 embryo has been taken from the egg. 



Make a sketch of the embryo as seen on the 

 fourteenth day, marking all the parts. 



The following is the process of hatching, briefly 

 described. Carefully observe same when the 

 chicks are hatching in the incubator. 



When ready to come out, the chick raises its 

 head and pierces the inner shell membrane, and 

 immediately starts breathing the air in the cham- 

 ber, which causes the pulmonary circulation to 

 become active and the embryonic circulation to 

 cease. The head is next raised into the air cham- 

 ber, and the chick deals blows upon the shell, 

 which when often repeated in the same place 

 result in fracturing it. This process is repeated 

 until the shell is broken around about one third 

 of the way from the large end. The chick then 



