COMPOSITION OF THE EGG 



401 



surplus matter, and naturally this demands a uniform chemical 

 composition. When the egg is first laid it is completely filled, 

 but as soon as it cools the contents contract and an air space or 

 air cell is formed. This cell usually lies between the two shell 

 membranes, and at the large end of the egg, where it is plainly 

 visible with the aid of a candle. As the age of the egg increases 

 evaporation takes place, which enlarges the air cell to consider- 

 able size, and therefore denotes, approximately, the degree of 

 freshness. 



The composition of hens' eggs is somewhat variable, with 



Fig. 261. — Class in candling, grading and packing eggs at the Kansas 

 Agricultural College. 



breeds and with individuals, and also as the result of care and 

 feeding. A general idea may be had from the following table: 



Albxwen 

 Whole Egg Yolk or White 



Water , 70 to 76% 46 to 52% 80 to 88% 



Fat 9 to 14% 30 to 35% Traces 



Protein 10 to 15% 14 to 16% 10 to 13% 



Shell and its membranes 9 to 12% .... .... 



The precise chemical analysis of a hen's egg is too technical 

 for the subject of this book, and it is really unimportant so far 

 as the average poultryman is concerned. The eggs of turkeys, 

 geese, ducks, guineas and other birds vary slightly from the above 

 table, and are, therefore, more desirable for certain purposes. 

 26 



