220 THE POULTRY-BOOK. 



One important part of the egg, which we have not hitherto 

 noticed, is the air-bag, or folliculus aeris of the anatomists, 

 placed at the larger end, between the shell and its lining mem- 

 branes. It is, according to Dr. Paris, about the size of the eye 

 of a small bird in new-laid eggs, but is increased as much as 

 ten times in the process of hatching. 



This air-bag is of such great importance to the development 

 of the chick, probably by supplying it with a limited atmos- 

 phere of oxygen, that, if the blunt end of an egg be pierced 

 with the point of the smallest needle, (a stratagem which mal- 

 ice not unfrequently suggests,) the egg cannot be hatched, but 

 perishes. 



Instead of one rudimental egg falling from the ovarium,two 

 may be detached, and will of course be enclosed in the same 

 shell, when the egg will be double-yolked. If these double- 

 yolked eggs be hatched, they will produce rarely two separate 

 chickens, but, more commonly, chickens with two heads and 

 the like. 



The shell v of an egg, chemically speaking, consists chiefly 

 of carbonate of lime, similar to chalk, with a small quantity 

 of phosphate of lime and animal mucus. When burnt, the 

 animal matter and the carbonic acid gas of the carbonate of 

 lime are separated, the first being reduced to ashes or animal 

 charcoal, while the second is dissipated, leaving the decarbon- 

 ized lime mixed with a little phosphate of lime. 



The white of the egg (albumen) is without taste or smell, 

 of a viscid, glairy consistence, readily dissolving in water, 

 coagulable by acids, by spirits of wine, and by a temperature 

 of 165 Fahrenheit. If it has once been coagulated, it is no 

 longer soluble in either cold or hot water, and acquires a slight 

 insipid taste. Experiments show that it is composed of eighty 

 parts of water, fifteen and a half parts of albumen, and four 

 and a half parts of mucus, besides giving traces of soda, ben- 



