THE CHICKEN. 



103 



men. In the centre is a yellow, spherical mass, the vitellus 

 or yolk, fixed in its position by very delicate ligaments 

 composed of the albumen twisted on itself. The vitellus 

 is formed of an agglomeration of very small vesicles en- 

 veloped by an exceedingly thin pellicle. Upon one point 

 of its surface is found a whitish rounded spot ; this is the 

 cicatricle, or germ of the young bird. During incubation 

 this germ develops, becomes organized, and absorbs for 

 its own nutrition all 

 the matter contained [ ' 



in the egg. The 

 white and the yolk 

 are only magazines 

 of nourishment. In 

 the egg of the 

 chicken these two 

 substances exist in 

 about equal propor- 

 tions. The white is 

 composed of thir- 

 teen per cent, of a 

 nitrogenized matter, 

 named albumen, and 

 eighty-seven per cent, of water. The yolk contains nine- 

 teen per cent, of a nitrogenous matter, called vitelline, 

 twenty-nine per cent, of a fatty matter, called egg-oil, 

 and fifty-one per cent, of water, with a small quantity 

 of a sulphurized matter. The decomposition of this 

 matter produces hydrogen sulphide, which gives the 

 characteristic unpleasant odor to rotten eggs. 



In the egg the bird finds nitrogenized and fatty mat- 

 ters, that is, all the elements necessary for its develop- 

 ment and the formation of its tissues, and the shell 



SECTION OF FOWL'S EGG. a, central plug of 

 white yolk ; 6, position of germinal area ; c, 

 yellow yolk ; d, white of egg ; e, " tread" or 

 chalaza; /, air-space between outer mem- 

 branes. 



