I stop there; for you surely know the list by this time!
Only the third aliment of nutrition remains to be considered, for there are but three; and I will tell you in confidence, what is stranger still, viz., that there is in reality but one! But we have had enough food for one day, and I do not wish to spoil your appetite. We will reserve the rest for another meal.
LETTER XXVII.
ALIMENTS OF NUTRITION (continued).
NITROGEN OR AZOTE.
There is a favorite conjuring trick, which always amuses people, though it deceives no one. The conjuror shows you an egg, holds it up to the light that you may see it is quite fresh, then breaks it; and—crack—out comes a poor little wet bird, who flies away as well as he can.
This trick is repeated in earnest by nature every day, under our very eyes, without our paying any attention to it. She brings a chicken out of the egg, which we place under the hen for twenty-two days, instead of eating it in the shell as we might have done, and we view it as a matter of course. Yet we do not say here that the bird may not have come down the conjuror's sleeve, or the hen may not have brought it from under her wing. It was really in the egg, and its own beak tapped against the shell from within and cracked it.
How has this come about? No one can have put that beak, those feathers, those feet, the whole little body, in short, into the egg while the hen was sitting upon it, that is certain. It is equally certain, then, that the liquid inside the egg must have contained materials for all those things beforehand; and if Nature could manufacture the bones, muscles, eyes, etc., of the chicken, out of that liquid while in the egg, she would probably have found no more difficulty in manufacturing your bones, muscles, eyes, etc., from it had you swallowed the egg yourself.
Here, then, is an undeniable aliment of nutrition.
It is called albumen, which is the Latin word for white of egg. It is easily recognized by a very obvious characteristic. When exposed to a temperature varying from sixty to seventy-five degrees of heat, according to the quantity of water with which it is mixed, albumen hardens, and changes from a colorless transparent liquid, into that opaque white substance, which everybody who has eaten "hard-boiled eggs" is perfectly well acquainted with.