had tasted those delicious little cheeses which are sold in the streets of Canton. They cannot be distinguished from our own. Only the Chinese (from whom we shall learn a great many things when we have beaten them so that they will conclude to be friends with us)—the Chinese, I say, do without milk altogether. They stew down peas into a thin pulp. They curdle this pulp just as we do milk, and in the same way they squeeze the curd well, salt it, and put it into moulds-just as we do—and out comes a cheese at last-a real cheese, composed of real casein! Put it into the hands of a chemist, and ask him the component parts of a hundred grains of it, and he will tell you as follows:

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, albu men 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.

I will only add one trifling detail. 100 ounces of albumen contain as follows:

You can fill up this number yourself, can you not? And knowing the 7 of hydrogen, you may guess what follows! After what we have talked of last time, here is already an explanation of the chicken's growth. But let us go on.

You recollect that yellowish liquid I spoke about, which lies underneath the clot, or coagulum of the blood? I will tell you its name, that we may get on more easily afterward. It is called the serum, a Latin word, which, for once, people have not taken the trouble of translat ing, and which also means whey. Put this serum on the fire, and in scarcely longer time than it takes to boil an egg hard, it will be full of an opaque white substance, which is the very albumen we are speaking of. Our blood, then, contains white of egg; it contains in

fact-if you care to know it-sixty-five times more white of egg than fibrine, for in 1,000 ounces of blood, you will find 195 of albumen, and only three of fibrine; of casein, none.

Nevertheless we eat cheese from time to time. And we generally eat more meat than eggs, and meat is prin cipally composed of fibrine! I should be a good deal puzzled to make you understand this, if we had not our grand list to refer to.

Fibrine, casein, albumen, they are all the same thing in the main. It is one substance assuming different appearances, according to the occasion; like actors who play several parts in a piece, and go behind the scenes from time to time to change their dresses. The usual appearance of the aliment of nutrition in the blood is albumen; and in the stomach, which is the dressing-room of our actors, fibrine and casein disguise themselves ingeniously as albumen; trusting to albumen to come forward afterwards as fibrine or casein, when there is either a muscle to be formed, or milk to be produced.

Know, moreover, that albumen very often comes to us ready dressed, and it is not only from eggs we get it. As we have already found the fibrine of the muscle and the casein of milk in vegetables, so we shall also find there, and that without looking far, the albumen of the egg. It exists in grass, in salad, and in all the soft parts of vegetables. The juice of root-vegetables in particular contains remarkable quantities of it. Boil, for instance, the juice of a turnip, after straining it quite clear, and you will see a white, opaque substance produced, ex

actly like that which you would observe under similar circumstances in the serum of the blood; real white of egg, that is to say—to call it by the name you are most familiar with-with all its due proportions of carbon, hydrogen, oxygen, and nitrogen.

I wonder whether you feel as I do, dear child; for I own that I turn giddy almost when I look too long into these depths of the mysteries of nature. Here, for instance, is the substance which is found everywhere, and everywhere the same-in the grass as in the egg, in your blood as in turnip-juice! And with this one sole substance which it has pleased the great Creator to throw broadcast into everything you eat, He has fashioned all the thousand portions of your frame, diverse and delicate as they are; never once undoing it, so to speak, to re-arrange differently the elements of which it is composed. From time to time it receives some slight impulse which alters its appearance but not its nature, and that is all. As the chemist found it in the bit of salad, so he will find it again in the tip of your nose, if you will trust him with that for examination. We are proud of our personal appearance sometimes, and smile at our selves in the looking-glass; we think the body a very precious thing; but yet when we look deeply into it we find it merely so much charcoal, water and air.

This reminds me that we have not yet made acquaint ance with the new personage who was lately introduced upon the scene. Nitrogen or azote, I mean. He plays too important a part to be allowed to remain in obscurity.

You have already learnt that oxygen united with hy drogen produces water. Combined with nitrogen it produces air; but in that case there is no union of the two. They are merely neighbors, occupying between them the whole space extending from the earth's sur