40 Composition of Eggs. 
Feeling ourselves the importance of making additions to the 
researches already brought forward on the composition of eggs, 
we have undertaken this task together, the questions which it 
raises being partly zoological and partly chemica 
subject so vast, which needs the continuous study of eggs of 
animals belonging to different classes of the animal kingdom, 
cannot be exhausted in one article; we are far too, from consid- 
ering our researches as completed. 
e propose in this memoir, to describe the differences ah 
exist in the composition of eggs, and to lay down some ger 
principles, to be developed in subsequent communications. 
1. Eggs of Birds. 
What we have said at the commencement of this article suffi- 
ciently explains our silence as to the composition of hen’s eggs 
during the evolution of the fetus, and as to former researches 
relative to the membranes which envelop the first formation of 
the chicken within the egg. We will here examine only the 
nature of the two substances, the white or albumen, and the yel- 
low or vitellus, in order to start from this point of comparison in 
studying the eggs of other animals. We shall not follow strictly 
the order established by zoologists for the animal series, though 
we shall not depart widely from that order. 
‘The composition of birds eggs has been clearly established by 
numerous authors, first by Vauquelin, Bostock, and then by Chev- 
reul, John, Dumas and Cahours, Lecanu, Gobley, Martin St.-Ange 
and Baudrimont, Scheerer. And in this part of our researches, 
we are satisfied to confirm the exactness of the leading facts an- 
nounced by the observers we have eticl and to determine with 
precision the specific characters of birds 
The white of birds egg is considered - almost all chemists as 
a principle itself pure, though this white has in it various salts 
and a sulphurous body which can be separated from the albumen | 
by different reagents without producing the aces of that 
substance, as was long ago shown by Chevreul. 
n examining the white taken from eggs a different kinds of 
birds, we have often noticed that this body has varying proper- 
ties. In some kinds, it is almost fluid; in others, it possesses a 
gelatinous consistency. The white of the egg of a hen is, after 
boiling, opaque, and of a pure color, white and solid. That o 
the wing becomes after cooking, transparent, opaline, green- 
ish, and so hard that it may be cut into little stones, used in cer- 
tain parts of Germany for common jewe 
__ These peculiarities are not enough to prove that the white of 
birds eggs is formed of different albumens, but they seem to show 
that attentive researches will enable us to point out new sie oa 
ties in these albumens, which have ve hitherto escaped chemists 
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