I.] THE WHITE OF THE EGG. 3 



Over the greater part of the egg the two layers of 

 the shell-membrane remain permanently in close appo- 

 sition ; but at the broad end they tend to separate, and 

 thus to develope between them a space into which air 

 finds its way. This air-chamber, as it is called, is not 

 to be found in perfectly fresh eggs, but makes its 

 appearance in eggs which have been kept for some 

 time, whether incubated or not, and gradually increases 

 in size, as the white of the egg shrinks in bulk from 

 evaporation. 



Immediately beneath the shell-membrane is the 

 white of the egg or albumen (Fig. 1, w.), which is, chemi- 

 cally speaking, a mixture of various forms of proteid 

 material, with fatty, extractive, and saline bodies. The 

 outer part of the white, especially in eggs which are not 

 perfectly fresh, is more fluid than that nearer the yolk. 



Its average composition may be taken as 

 12'0 p. 0. proteid matter, 

 1'5 p. 0. fat and extractives, 

 5 p. 0. saline matter, chiefly sodic and potassic chlorides, 

 with phosphates and sulphates, 

 86'0 p. 0. water. 



The white of the egg when boiled shews in section alter- 

 nate concentric layers of a transparent and of a finely granular 

 opaque material. In the natural condition, the layers corre- 

 sponding to these opaque layers are composed of more fluid 

 albumen, while those corresponding to the transparent layers 

 are less fluid, and consist of networks of fibres, containing fluid 

 in their meshes. The innermost layer, however, immediately 

 surrounding the yoUc (Fig. 1, x.), is of the more fluid finely 

 granular kind. 



In eggs which have been hardened a spiral arrange- 

 ment of the white may be observed, and it is possible to 



1—2 



