INCUBATION. 223 



At the end of two hundred and thirty-six hours,. the bill 

 assumes a green color, and, if the chick be taken ot of the 

 egg, it will visibly move. 



At two hundred and sixty-four hours, the eyes appear ; at 

 two hundred and eighty-eight hours, the ribs are perfect ; and 

 at three hundred and thirty-one hours, the spleen approaches 

 near to the stomach, and the lungs to the chest. 



At the end of three hundred and fifty-five hours, the bill fre- 

 quently opens and shuts. 



At the end of the eighteenth day, the first cry of the chicken 

 is heard ; and it gradually acquires more strength, till it is 

 enabled, as we shall presently see, to release itself from con- 

 finement. 



Some people, upon the eleventh or twelfth day, examine the 

 eggs which have been sitten upon, to pick out the bad ones. 

 With this view they place the eggs on a drum, or between the 

 hands, in the sunshine, and observe the shadow. If this 

 wavers, by the motion of the chick, the eggs are good ; if the 

 shadow shows no motion, they throw them away. 



EXCLUSION OF THE CHICK. 



About the twenty-first day, the chick is excluded from the 

 egg, whose shell is not broken by the hen, as is sometimes 

 ignorantly asserted, but by the chick itself, in a highly inter- 

 esting process, first investigated by M. Reaumur, though it 

 was known to Albertus Magnus in the thirteenth century. 



For the purpose of breaking the shell, the chick is furnished 

 with a horny-pointed scale, greatly harder than the bill itself, 

 at the upper tip of the bill a scale which falls off after the 

 chick is two or three days old. The chick is rolled up in the 

 egg in the form of a ball, with its fore part towards the biggest 

 end, and its beak uppermost, with the hard scale nearly touch- 

 ing the shell 





