PRAIRIE FARMER'S POULTRY BOOK 



follicle cleaves and allows it to escape. By some strange 

 attraction it is drawn to the mouth of the oviduct, known as 

 the infundibulum, and enters the tortuous tube where its 

 development is carried on to completion. 



The walls of the oviduct are lined with a network of blood 

 vessels which furnish the material for the further development 

 of the egg. In the upper portion of the oviduct the albumen 

 is secreted and deposited around the yolk in layers. In the 

 middle portion and toward the lower end, the two membranes- 

 are formed around the albumen. The outer membrane is 

 covered with carbonate of lime, which is secreted and deposited 

 just before the egg passes into the cloaca. This is called the 

 shell of the egg. 



The cloaca is a pouch at the end of the oviduct sufficiently 

 large to receive the egg. Here a secretion is formed and de- 

 posited upon the shell. This film in a measure makes the shell 

 impervious to germs and other harmful substances and pre- 

 vents the evaporation of the egg contents. The egg is now 

 fully formed and ready to be laid. The time required for the 

 development of the yolk in the ovary is about three weeks ; 

 but, after the egg enters the oviduct, only 18 hours are re- 

 quired for its completion. It is evident, therefore, that two 

 eggs may be in the oviduct at the same time, especially during 

 the height of the laying season. 



Structure of an Egg 



The accompanying diagram illustrates the structure of a 

 normal egg. Beginning with the outside, an enumeration of 

 the various structures comprises the following : 



1. The shell, porous to admit air and hard for protection. 



2. Exterior membrane, a tough membrane calculated to exclude 

 germs and harmful substances. 



3. The inner membrane immediately surrounding the albumen. 

 This envelops the developing chick and turns with the chick as it pips 

 the shell. The air space at the large end of the egg is between the two 

 membranes. 



4. The albumen, or white, of the egg, which is formed in concen- 

 tric layers around the yolk. 



5. Vitelline membrane, a delicate membrane surrounding the yolk. 



6. Dense layer of albumen. This is just outside the vitelline mem- 

 brane. 



7. Yolk, the yellow layers of albumen just -within the vitelline mem- 

 brane. The yellow color is due to globules of fat. The white yolk is in 

 the center surrounded by the yellow yolk. 



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