14 BlGGlvK POUI/TRY BOOK. 



branes H, like a mariner's compass, so that the germ 

 always retains its position on top of the yolk. While 

 this germ is present in all eggs alike, it requires the 

 contact of the male element to give it vitality. This 

 contact takes place in the oviduct before the yolk is 

 surrounded by the white, or albumen, and the shell. 



The yolk is the essential part of the egg, contain- 

 ing as it does the germ, and albuminous and fatty 

 matter and organic salts sufficient to support the germ 

 in its earlier stages of development. The white, 

 which is pure albumen and water, furnishes in the first 

 place a safe and congenial medium for the preserva- 

 tion of the life germ and afterwards contributes its 

 share of nutriment to the developing embryo. 



The shell is a layer of carbonate of lime deposited 

 so as to give the greatest possible strength, and so ar- 

 ranged as to leave numerous pores through which the 

 water of the egg can escape and the external air can 

 enter. 



About three-fourths, 74 per cent., of the contents 

 of an egg consist of water, 14 per cent, is albumen, 

 10.5 per cent, is fat, and 1.5 per cent, is ash. Of the 

 latter the principal part consists of phosphate of lime, 

 the element that enters so largely into the composi- 

 tion of bones. 



These constituents of an egg furnish every ele- 

 ment, except oxygen, essential to the formation of 

 the living bird. 



The egg is the beginning of all animal life. In 

 the case of mammals, this egg is hatched and the 

 young animal is nourished and developed for a certain 

 period within the body of the mother before it is cast 



