398 CHEMISTRY. 



563. Formation of the Bird in the Egg. In the formation 

 of the bird in the egg we have a marked illustration of the 

 prominent part which albumen plays in nutrition. Both 

 the yolk and the white are composed chiefly of albumen 

 dissolved in water. The white is seven eighths water, and 

 only one eighth albumen. In the yolk we have the same 

 solution of albumen holding yellow globules of oily matter 

 suspended in it. There are in both the yolk and the white 

 minute amounts of various mineral substances, as common 

 salt, phosphate of lime, carbonate of soda, etc. These form 

 the ash of the egg when it is burned. It is the albumen 

 of the egg from which all the varied structures of the bird 

 are formed the muscles, the skin, the feathers, etc. The 

 oily matter of the yolk, it is true, is diffused in the inter- 

 stices of many of the tissues, but it does not really form a 

 part of them, unless it be in the case of the brain. The 

 phosphate of lime also is deposited in the texture of the 

 bones, but it is the albumen that first forms that texture. 

 As we look at the white of an egg, so simple is it that we 

 can hardly believe that such a variety of tissues can be 

 evolved from it by the chemistry of life. And yet the ev- 

 idence is clear that it is so ; for shut up in the shell noth- 

 ing can gain admission to it but the oxygen of the air, 

 which acts upon it through the pores of the shell, and 

 thus materially aids in the process, as may be proved by 

 the interruption of it by a coat of varnish shutting up the 

 pores. 



5G4. Gelatin. There is considerable doubt as to the nat- 

 ure of this substance, which enters largely into the struct- 

 ure of some portions of animals. It is supposed that it is 

 formed from albumen and fibrin, as the gelatinous struct- 

 ures are well developed in animals which are fed upon these 

 substances alone. Its composition is nearly the same as 

 theirs, although its properties are very different. It forms 



