What Is An Egg? 21 



Whatever way the egg is turned the yolk quickly assumes its natural 

 position. The yolk, containing a large amount of fat, is lighter than 

 the albumen, therefore has a tendency to float at the surface, which during 

 incubation allows the young germ of life, which is on the surface of the 

 lightest portion of the yolk, to float in the warmest portion of the egg, 

 which is in contact with the body of the incubating hen. 



The yolk is covered by the "vitelline" membrane (11). The yellow 

 liquid within the membrane is called the "vitellus," which is used for the 

 most part to nourish the young chicken just before and for several days 

 after it hatches. The color of the yolk depends upon the kind of food fed. 

 Yellow corn and green food produce a deep colored yolk, while oats, 

 wheat and buckwheat produce a light yellow, due to the absence of color- 

 ing pigment in the grain. One of the first signs of weakened vitality in 

 hens is a tenderness of the vitelline membrane, which often ruptures when 

 eggs are roughly handled. This allows the vitellus to escape and mingle 

 with the white. The yolks therefore of perfectly fresh eggs from such 

 hens will rupture even when the egg is carefully broken. Keeping eggs 

 weakens the vitelline membrane. 



Just under the vitelline membrane, and at the surface of the yolk, is 

 the "germinal vesicle," Fig. 1 (12), the vital life principle of the egg. With- 

 out fecundation by the male no life would be developed in the germinal 

 vesicle, and the egg would be infertile. If fecundation should take place 

 and the hen should not be in vigorous condition, life would not necessarily 

 be developed. Infertility is due quite as much to lack of vital force of 

 the hen, because of close confinement, excessive laying or improper feed- 

 ing as to any fault of the male. 



Fecundation cannot take place until the yolk has burst from the 

 tough skin of the follicle. Fig. 1 (5), has entered the oviduct. Fig. 1 (7). 

 Here it comes in contact with the "spermatozoa" of the male, which there 

 swarm and live for several weeks, growing less numerous and less active 

 with age. The spermatozoa penetrate the vitelline membrane, unite with 

 the germinal vesicle and life is begun. If the egg should be retained 

 for any considerable time, which often happens, the body heat will start 

 the process of incubation, which will continue until the egg is placed in 

 a temperature too cold for development. Eggs which are not fertile will 

 therefore continue without danger of incubation in a temperature that 

 would allow life to develop with a fertile t^g. 



After the albumen has been secreted in the part of the oviduct. Fig. 1 

 (9), it is pushed along to a point where the shell membrane is formed, it is 

 supposed somewhere at or between 13 — 14 Fig. 1, after which another 

 membrane is added. Then the egg passes to position marked 14 Fig. 1, 

 and Fig. 2 (2), where the glands secrete a liquid which contains carbonate 

 of lime and other mineral matters. This hardening process is completed 



