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COMMERCIAL POULTRY RAISING 



with little white dots in the center, it is fertile. The infertile 

 germ is whitish in appearance and lacks the clear outer ring. 



The activity of this life germ is temporarily suspended as soon 

 as the egg is laid. But as soon as the egg becomes heated to the 

 proper temperature, either by contact with the hen's body or by 

 other means, its development is resumed. It has been found that 

 this germ contains no definite organs, but that its function is to 

 reproduce other cells like itself, each enlarging and reproducing 

 more cells with the same functions, which ultimately establish 

 the form and body of the chick. 



Signs of Life. — After about 24 hours' incubation life is per- 



Dead Germ Fertile Egg Infertile Egg 



^California Experiment Station) 



Fig. 168. — Appearance of hatching eggs through candle on seventh day of in- 

 cubation. 



ceptible, but only if the egg is broken open. Blood-vessels may 

 be seen, and on the third day the heart appears. On the fourth 

 day the eye can be distinguished, and from the eye and heart 

 blood-vessels radiate in all directions, which, to the mind of the 

 Candler, resemble a sort of spider. See Fig. 168. This network 

 of blood-vessels continues to grow until it completely surrounds 

 the shell membrane. Its function is to take up oxygen penetrat- 

 ing the shell, and act as a respiratory apparatus until the lungs 

 are completed on or about the nineteenth day. 



The lungs start to take form on the fifth day, and on the seventh 

 day the bill is noticeable. The bones are pretty well shaped by 



