446 LIQUID PARTS OF ANIMALS. 



CHAPTER X. 



OF THE EGGS OF FOWLS. 



THE eggs of all birds, so far as they have been examined, bear 

 a striking resemblance to each other. They consist of four parts, 

 1. The shell, which is white in the eggs of the common fowl, and 

 of many other birds ; but it is often coloured or spotted of va- 

 rious colours, so as to give it a beautiful appearance. 2. The 

 membrana putaminis, a thin translucent pellicle immediately 

 within the shell. At the great end of the egg this membrane is 

 detached from the shell, leaving a certain distance between them, 

 which is filled with air. 3. The white or albumen, a glairy liquid 

 consisting of albumen dissolved in water, and contained, like the 

 vitreous humour of the eye, in an extremely thin membrane di- 

 vided into cells. 4. The yolk, a thick and almost solid yellow 

 matter, inclosed in a peculiar membrane. This membrane, by 

 two ligaments called chalaza, is tied to the membrane of the al- 

 bumen, and thus the yolk is kept in the centre of the egg. 



1. The shell of the common fowl was analyzed by Vauquelin* 

 and Merat Guilokf But both of these chemists seem to have 

 overrated the quantity of animal matter which it contains. Ac- 

 cording to Dr Prout's analyses, which seem to have been con- 

 ducted with scrupulous attention to accuracy, its constituents 

 are, 



Carbonate of lime with a little carbonate ) Q- 



of magnesia, . / 



Phosphate of lime and magnesia, . 1 



Animal matter, . . 2 



100| 



2. If we suppose the weight of the whole egg to be 1000 

 grains, the average weight of the membrana putaminis will be 

 2-35 grains. This membrane has not been subjected to analy- 

 sis. According to Hatchett it consists of coagulated albumen. 



* Ann. de Chim. Ixxxi. 304. 



f Ann de Chim. xxxiv. 71. | Phil. Trans. 1822, p. 381. 



Prout, Ibid. 



