EGGS IN CHEMISTRY AND COMMERCE. 



97 



The yolk contains water and albumen, but associated "with, 

 these is quite a large number of mineral and other substances, 

 which render it very complex in composition. The bright yellow 

 color is due to a peculiar fat or oil, which is capable of reflecting 

 the yellow rays of light, and this holds the sulphur and phos- 

 phorus which abound in the egg. 



It is well known that from the egg all the constituent parts of 

 the young animal are formed — its skeleton, as well as its various 

 soft textures. Now, for the construction of the skeleton an amount 

 of earthy matter is required which does not exist preformed in 

 the soft contents of the egg, but has to be drawn from the shell. 

 During the process of incubation, with the co-operation of the 

 atmospheric air which permeates the shell, it appears that the 

 phosphorus present in the yolk gradually undergoes oxidation, 

 and becomes converted into phosphoric acid. This acts upon and 

 dissolves the carbonate of lime belonging to the shell, which thus, 

 as incubation proceeds, becomes thinner and thinner. The thin- 

 ning of the shell also makes it easier for the young bird to peck 

 its way out. 



An enveloping membrane or bag surrounds the yolk, and 

 keeps the fluid matter of which it is composed together. Being 

 lighter than the white, it floats to that portion of the egg which 

 is uppermost, but is kept in position between the two extremities 

 by two processes of inspissated albumen, called chalazea, which 

 pass to and are attached, one to either end of the egg. 





Entire contents. 



White. 



Yolk. 



Nitrogenous matter 



14-0 



10-5 



1-5 



74-0 



20'4 



1-6 



780 



16-0 





30-7 





1*8 





62-0 







Total 



100-0 



100-0 



1000 







The white of egg, as this shows, contains a considerably larger 

 proportion of water than the yolk. It contains no fatty matter, 

 but consists mainly of albumen in a dissolved state, and inclosed 

 within very thin-walled cells. It is this arrangement which gives 

 to the white of egg its ropy, gelatinous state. Thoroughly shak- 

 ing or beating it up with water breaks the cells and removes the 

 ropy state. 



Eggs are useful for many purposes besides food and hatching. 

 The white of an egg has proved a most efficacious remedy for 

 burns ; seven or eight successive applications of this substance 

 soothe the pain and effectually exclude the air from the burn. 

 This simple remedy seems preferable to collodion, or even cotton. 

 Extraordinary stories are told of the healing properties of an oil 



VOL. XXXV. — 7 



