CHAPTER XLII 

 EGGS AND INCUBATION 



The egg is an object of much interest, for it is not only 

 the source of the chicken itself, but also a most important 

 source of income to the poultryman. If one is to handle 

 the egg intelligently, one must know something of its com- 

 position, of how the chick is developed within the shell, and 

 of commercial differences and values. 



The parts of the egg of special interest are five: 



The shell, composed mostly of lime, and hard enough to 

 enclose and protect the softer interior. 



Two tough membranes lying next within the shell. These 

 separate at the large end, forming a small air sac, which is 

 easily seen in hard-boiled eggs. 



The albumen, or, as it is commonly called, the white of 

 the egg. This forms about 57 per cent of the egg and con- 

 sists of much nitrogenous matter of a liquid, sticky, trans- 

 parent character.. Boiling hardens, or coagulates, the white 

 into a firm, white structure. 



The yolk, comprising about 33 per cent of the egg, is a 

 round yellow sac, surrounded by the white. This is used 

 for nourishing the young chick just before and after leaving 

 the shell. The yolk is suspended midway in the white and 

 kept in proper position by two albuminous cords. 



The blastoderm in the fresh-laid egg is seen as a white 

 speck about one eighth of an inch in diameter on the upper 

 side of the yolk. The blastoderm is the true egg and 

 source of the chick in incubation. 



The fertile egg is one that will produce a chick under 

 proper conditions of what is called incubation. The infertile 

 or sterile egg can not be hatched, and so has no value in 



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