SECT. I] PHYSICO-CHEMICAL SYSTEM 265 



1-6. The Avian Egg-white 



The white of the egg is divisible into three portions which have 

 been studied separately by Romanov. The outermost and thinnest 

 layer makes up 39-8 % of the whole and has 1 1'6 % dry solid. The 

 middle layer accounts for 57-2 % and has 12-4% dry solid, and the 

 innermost, thickest, layer is only 3 % and has i4'5 % dry solid*. The 

 chalazae have only once been analysed separately (Liebermann), 

 when the elementary composition of their protein was ascertained. 

 Table 1 2 summarises the results of the investigators who have made 

 general analyses of the white. It is a very watery solution of 

 protein, containing only the most negligible traces of fats and 

 lipoids, but a great many water-soluble substances such as carbo- 

 hydrate in various forms, protein breakdown-products, choline, 

 inositol, etc. Natural egg-white, according to Rakusin & Flieher, 

 is a saturated solution of ovoalbumen (15-35 P^^ cent.). The 

 water-content does not vary much, but Tarchanov's analyses go 

 to show that the smaller eggs with short incubation-time are 

 wetter than the others. The proteins of the egg-white are believed 

 to be variable in number in the eggs of different birds. In that 

 of the hen, four are known, in that of the crow three, and in that 

 of the dove one only. The egg-white of the hen's egg contains two 

 albumens, ovoalbumen and conalbumen, and two glucoproteins, 

 ovomucoid and ovomucin. 



It was at one time thought that there was a fifth, ovoglobulin. 

 Dillner studied it in 1885, and estimated that it made up 0-67 per 

 cent, of the egg-white and 6-4 per cent, of the total protein, but 

 Osborne & Campbell showed that it was simply a mixture of the 

 others in different proportions. This had already been made probable 

 by the results obtained by Corin & Berard, who were able to separate 

 the ovoglobulin into two or three constituent proteins having 

 several different coagulation temperatures (57*5°, 67°, 72°, 76° and 

 82° C.) and other special characteristics. 



Hofmeister was the first to prepare crystalline ovoalbumen, and 

 he published several papers on it. Other workers confirmed his dis- 

 covery, such as Gabriel ; Harnack ; and Bondzynski & Zoja, but 

 Hopkins & Pincus showed that the albumen so crystallised only 

 accounted for half the protein present in the egg-white. Part of the 

 missing protein was found by Osborne & Campbell to be in the 



* A large number of concentric rings can be seen in egg-white coagulated in situ, 

 according to Remotti. 



