284 N EGG FAKM. 



fluctuations of the temperature of the egg are not neces- 

 sary to secure it, as was formerly supposed. The benefi- 

 cent oxygen of the air and the injurious carbonic acid 

 gas, or carbon dioxide as the shorter and preferable term 

 is, exhaled from the embryo as it grows, will exchange 

 places through the shell and mix, urged by a force or 

 tendency inherent in their nature. Chemistry teaches 

 that this force needs no assistance from the alternate 

 expansion and contraction of the contents of the egg 

 consequent on heating followed by cooling, though 

 poultry men once universally believed this assistance 

 necessary. 



TURNING THE EGGS. 



While cooling the eggs is to be avoided, turning them 

 is absolutely indispensable, as abundant experiments 

 have shown. The hen does not turn them systematic- 

 ally at all. Her efforts are limited to shifting them 

 from the outer edge of the nest to the center, and in 

 accomplishing this purpose she necessarily turns them 

 more or less. They may turn halfway over, or three- 

 quarters, or perform one or more complete revolutions, 

 and possibly, though not probably, land in the same 

 position as before starting. There is no "this side up 

 with care," but they take their chances, and, as the hen 

 rolls some of 'them, if not all, several times in twenty- 

 four hours, by the laws of chance they are prevented 

 from always landing on the same side even if they some- 

 times do. 



In addition to the rolling performed with her beak, 

 she moves nearly all the eggs a little while settling down 

 on returning from a foraging expedition, on which occa- 

 sion she makes a careful though quite vigorous shuffling 

 to give room for her feet and shanks. The hen, unless 

 very tame, does not ordinarily meddle with her eggs 

 when you are watching her, but when alone repeats her 



