96 HATCHING AND REARING 



itself and adheres to it, and the inner one is closely adherent 

 to the outer. Examination of an egg a few days old will 

 show that at the large end these two membranes are de- 

 tached from each other and that there is a small air space 

 between them. This is commonly called the air cell. As 

 evaporation takes place the air cell grows larger, because 

 the liquid evaporated leaves more room for the outside air, 

 which finds its way in at the large end. Sometimes the air 

 cell may be misplaced, being often found on the side of the 

 egg. This is because the egg is old, and has been lying on 

 its side for a long time; the heavy liquid has settled at the 

 bottom and the air cell risen to the top. At hatching time 

 the shell membranes should be soft and easily broken; if 

 dry and rough, the hatch will be poor, for the chicks cannot 

 pick their way out of the shell. These membranes are com- 

 posed largely of nitrogenous material. Lying immediately 

 under the shell membranes are dense layers of a white sub- 

 stance called egg albumen, which contains considerable 

 nitrogen or protein, has no smell, and very little taste. The 

 white of the egg readily coagulates, and when an egg is 

 dropped into boiling water, this process of coagulation may 

 be easily seen. A study of the egg shows three distinct 

 layers of albumen. First, is a thin liquid near the shell; 

 next, in the center of the egg surrounding the yolk, is a very 

 heavy, dense layer; and a medium layer lies between the 

 two. Egg albumen has two distinct functions to perform. 

 First, it acts as a protective cushion around the chick during 

 its development, preventing sudden jars and shocks. Its 

 main function, however, is to provide the growing chick in 

 the shell with nutriment which goes directly into the forma- 

 tion of its body. At each end of the egg, in the albumen, 

 will be found a thickened string or cord, «'hich appears to 

 be twisted, and attached to each end of the yolk. These 

 cords are called the albumen cords or chalazse. Their 

 function is to hold the yolk suspended in the center of the 



