219 



An egg not impregnated by the male, will never 

 breed young, but always putrify. One impregnated 

 contains the rudiments of the bird, even before incu- 

 bation. By the microscope we see the plain carina 

 or spine of it swimming in the middle of the cicatri- 

 cula, consisting of fine white threads, which incuba- 

 tion gradually perfects. 



The air-bag is very small in a new laid egg, but 

 becomes larger, when the egg is kept. The yolk is 

 specifically heavier than the white. Hence its smal 

 ler end is always uppermost in all positions of the 

 egg- 



After incubation, the air-bag gradually extends, till 

 near the hatching, it takes up a third of the egg. By 

 incubation the white becomes thinner and more tur 

 bid, especially near the air-bag where it is first con 

 sumed. Then it lessens towards the sharp end of the 

 ejjg, till nothing is left, but a white,chalky substance. 

 The white of an impregnated egg is as sweet all the 

 time of incubation as that of a new laid-egg. They 

 are only unimpregnated eggs 5 vulgarly called wind. 

 eggs, which putrify and stink. 



The yolk also remains fresh and uncorruptcd all 

 the time of the incubation. It is depressed in the 

 middle, as the chick grows, and is soon brought into 

 a form, not much unlike that of a horse shoe, in the 

 middle of which the chick lies. 



Not long before ihe chick is hatched, the wholeyolk 

 is taken into the abdomen. 



The eye or tread, in which the chick lies, ia 

 soon enlarged by incubation, and rises to the upper 

 part of the egg. The heart and umbilical vessels, 

 are some of the first parts, which we are able to dis* 

 tinguish. 



