152 



HABITS OP BIRDS. 



to appear, and the body extends to one-third of an 

 inch in length. Several other important organs now 

 become visible, as the stomach, the intestines, and 

 the liver. A vascular membrane begins to form about 

 the navel, and grows during- the succeeding days so 

 rapidly that it covers almost the whole inner surface 

 of the shell, apparently performing the office of lungs 

 in carrying on the process of respiration. 



On the fifth day the lungs begin to be formed, 

 but cannot, of course, perform their functions, on 

 account of the circumambient fluid. The vessels of 

 the navel rise out of the abdomen ; the heart is con- 

 fined in a very thin membrane that covers the chest; 

 and the muscles appear over the body in the form of 

 an unctuous envelope. 



An Egg as it appears five days after incubation, with a magnified view of 

 the Chick. 



On the sixth day the gall-bladder is first per- 

 ceptible, and the first indications of voluntary motion 



