Relative Amount of Mucin in Thick and in Thin Egg White

The white of a hen's tgg is readily separated into two portions, the thin white and the thick white. The yolk appears to be floating in thin white enclosed in a sac of thick white and this thick white is suspended in another (outer) layer of thin white. Previous studies of tgg white have not demonstrated the nature of the difference between thick and thin white. In studying the proteins of egg white we have found that the thick portion of the white contains a much higher proportion of a protein possessing the properties of mucin than the thin white. This protein is soluble in an excess of mineral acids, insoluble in an excess of acetic acid, has a low nitrogen content (12.9%), and has the general physical properties of mucn. Examination of the eggs of some other birds indicates that this unequal distribution of mucin is not confined to the egg of the hen. Table I shows the mucin content of the eggs of the hen, pigeon and duck. The whites of the eggs were separated on a screen as described by Hoist and Almquist. The thin white separated by this method contains both the outer and inner thin whites. Tests of the inner thin white indicate that it may contain only minute quantities of mucin. It is possible that in the formation of eggs the mucin secretion and the serous secretion are poured out together and that the mucin particles coalesce, holding a certain amount of thin white, and that the volume of thick white varies with the changes in hydrogen-ion concentration. Various authors, when discussing the preparation of the proteins of eggs, refer to the fact that they have dissolved egg white in salt solution or in water.