THE HATCHING EGG 109 



which time the lungs and respiratory organs also make their 

 appearance. The legs and wings are visible on the fourth 

 day. From this time on, these organs grow steadily and 

 gradually assume more and more the appearance they 

 will have at hatching. By the seventh day, the head and 

 body of the chick have attained a large size, the eye being 

 especially prominent. The feathers can be readily seen on 

 the ninth day, looking like little hairs all over the body. On 

 the fourteenth day the embryo can be seen to move about 

 in the egg, its head lying at the large end near the air cell, 

 and its feet being curled up in the small end. 



Eggs which contain a growing embryo should be candled 

 frequently in order to view them through the shell, and some- 

 times they should be broken to study the internal appearance. 

 The air cell rapidly increases in size, being as large as 

 a quarter on the fourteenth day. On the twentieth day the 

 embryo fills the entire cavity of the egg, with the exception 

 of the air cell. That part of the yolk which has not been 

 used by the embryo will be absorbed into the chick's body 

 on the nineteenth day, and will furnish its feed the first 

 few hours after hatching. 



Hatching. — If the egg is fertile and the proper temperature 

 be maintaiaed, hatching should take place on the twenty- 

 first day. This process is very interesting to young people. 

 The chick emerges from the shell in the following way: On 

 about the twentieth day it ruptures the membrane of the 

 iimer shell and pushes itself up, so that its head occupies 

 the cavity which was previously the air cell. The chick 

 then breathes the air, and is strengthened for its attack 

 upon the shell, which it breaks by hitting it tap after tap 

 in one place with its beak. After one small hole is punctured 

 the chick renews this tapping process around the shell until 

 it has cut all around the upper or large end. Then, by bracing 

 its head against this lid, and pressing with its feet against 

 the lower or small end, it ruptures the remaining shell, and 



