The Air-bag of the Egg. 43 



said experienced poultry-keepers can tell by the shape of 

 the eggs alone the hen that laid them ; for, strange to say, 

 however different in size the eggs of any particular hen 

 may be occasionally, they are very rarely different in form. 

 Among the most remarkable eggs may be mentioned those 

 of the Shanghae, or Cochin-China fowl, which are of a 

 pale chocolate colour ; and those of the Dorking fowl, 

 which are of a pure white, and nearly as round as balls. 

 The eggs of the Malay fowls are brown ; those of the 

 Polish fowl, which are very much pointed at one end, are 

 of a delicate pinkish white ; and those of the Bantam are 

 of a long oval." 



A very important part of the egg is the air-bag, or 

 foliiculus ceris, which is placed at the larger end, between 

 the shell and its lining membranes. It is, according to Dr. 

 Paris, about the size of the eye of a small bird in new laid 

 eggs, but enlarges to ten times that size during the process 

 of incubation. " This air-bag," says Mr. Dickson, " is of 

 such great importance to the development of the chick, 

 probably by supplying it with a limited atmosphere of 

 oxygen, that if the blunt end of the egg be pierced with 

 the point of the smallest needle (a stratagem which malice 

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

 perishes." 



An egg exposed to the air is continually losing a portion 

 of its moisture, the place of which is filled by the entrance 

 of air, and the egg consequently becomes stale, and after a 

 time putrid. M. Reaumur made many experiments in 

 preserving eggs, and found that, by coating them with var- 

 nish, it was impossible to distinguish those which had been 

 kept for a year from those newly laid ; but varnish, though 

 not expensive, is not always to be had in country places, 

 and it also remained on the eggs placed under a hen and 

 impeded the hatching, while in boiling them, the varnish, 

 not being soluble in hot water, prevented them from being 

 properly cooked. He tried other substances, and found 

 that fat or grease, such as suet, lard, dripping, butter, and 

 oil, were well adapted for the purpose, the best of these 

 being a mixture of mutton and beef suet thoroughly melted 



