fabricates the bile-it is an organ therefore; the bones are the framework which support the weight of the body

-so organs; the muscles are the power which sets the bones in movement-organs also, therefore; the skin is the armor which protects them-so an organ: in fact everything within us is an organ. If there was any corner of our body which was not an organ, it would be useless to us, and we should not, therefore, have received it, because God makes nothing without a usc.

Here lies the secret of that great miracle which is called life. I do not know whether you will be able to understand me thoroughly, but open your ears, as if some one was going to explain addition to you; this is not more difficult.

Life is in reality the total of an addition sum. Each one of our organs is a distinct being which has its particular nature and special office; its separate life consequently; and our individual life is the sum total of all these lesser lives, independent one of the other, but which nevertheless blend together by a mysterious combination, into one common life, which is everywhere and nowhere at the same time. It follows from this, that the more organs a being has, the greater is the sum total; the more, consequently, is life developed in him. Remember this when we begin to study life in the lower animals. In proportion as you find the number of organs diminish, you will find life diminishing in power, until we arrive at beings who have, as it were, only one organ apparent, and whose life is so insignificant, that we have some difficulty in giving an account of it, and are saying the utmost that can be said in calling it life at all.

But this comparison of life to the total of an addition sum, is too dry; and, although it has its appropriate side, yet it might give you a false idea of life; which is what

always happens when one tries to solve inscrutable ques tions and hidden mysteries by a matter-of-fact illus tration.

Let us try for something more to the purpose.

I told you that the Greek word organon was applied especially to instruments of music. Well, let us consider our organs as so many musical instruments. You have, probably, sometimes been at a concert. Each of the instruments in the orchestra performs its own part, does it not? The little flute pipes through all its holes; the double-bass pours thunder from its chords: the violin sighs with his; the cymbals clash; the Chinese bells dance to their own tinkling; all go at it in their own fashion, each independently of the other. And yet, when the orchestra is in good tune together, and well played, you hear but one sound; and to you the result of all these various noises, each of which would have no meaning alone, is music composed by some great artist whom you do not sec. It is no longer a flute, a double-bass, or a violin which you hear; it is a symphony of Beetho ven's, an oratorio of Haydn's, or Mozart's overture to Don Juan.

Life is just like this. All the instruments are playing together, and there is but one music; music written by God.

But wait! when I say life is just like this, let us come to an understanding. Life is something like it, that is all, for as to telling you what life is, I shall not attempt it. I know nothing about it, do you see, though that is a painful confession to have to make to a pupil; but in this case it does not distress me, and you are welcome to hunt the world through for a master, who in this matter docs know anything. I could make a hundred other comparisons, but they would all fail in some point or

other. Shall I tell you where this one fails? In an orchestra there is always a musician by the side of the instrument. Now with us we see the instrument well enough, but we cannot see the musician.

You are inclined to ask me, perhaps, why I am wast ing so much paper to-day in talking to you about organs, instead of going on tranquilly with our little history of the circulation. But I told you just now that the secret of life lies in the organs, and before entering upon the history of life, I ought to have begun with them. It is there all the books begin which treat of the subject we are studying together, and if you had one in your hands at this moment, it would teach you that all creatures whatsoever are divided into those which have organs and those which have none—that is, into organic and inor ganic beings* (in stands here for not, as incompleto means not complete).

This is, in fact, the starting point for the study of nature, and there are many other things besides which I ought to have told you before I began. But we went straight ahead, without looking at what we were leav ing behind, satisfied with turning aside from time to time to pay our debts.

And while I am making my confession, I ought to tell you all. You would probably only have listened to me with half an ear, if I had begun at the beginning. There is a proverb which says "The appetite comes with eat

* A lump of iron is the same throughout. Each of its parts has the same properties and the same uses. It has no organs, it is an inorganic being. A rose tree has flowers, which are differently made from its leaves, and serve a different use: a root which sucks up the precious food of the earth; a bark which is of a different nature from the wood, and serves a different purpose. It has organs; it is an organic being: all animals and vegetables are organic beings.

ing." I do not advise you to follow this proverb too closely at dinner, for it might mislead you sadly. But it is always true when applied to learning; it is what one knows already that gives one a taste for learning more. If I have been making you bite at the organs to-day, which is rather a tough morsel, it was because I fancied that your appetite had begun to come. Was I wrong?

Let us now return to the blood which nourishes the organs.

LETTER XVII.

ARTERIAL AND VENOUS BLOOD.

It is at the extremity of the capillary arteries, as we have said, that the incomprehensible prodigy of the nourishment of our organs is accomplished. This done, the next thing is for the blood to return to its startingpoint; and here recommence those infinitesimally minute wonders of which we have already spoken. Close upon the capillary arteries follow the capillary veins, equally fine and imperceptible as the others. These take possession of the blood everywhere at once, without allowing it a moment's respite, and it is thenceforth on its road of return, travelling back again to the heart.

Where do the veins begin? where do the arteries end? No one can say precisely, since the last ramifications of each elude the eye of man, however much it may be aided by the admirable instruments which his genius has invented. Nevertheless, although no one has ever ascertained the fact by sight, there is one thing I can tell you-namely, that our minute veins are a continuation of our minute arteries, and that it is the same canal which as it lengthens out turns from an artery into a vein, without any interruption; the substances destined for the nourishment of the organs passing through its walls, as moisture passes through our skin when we perspire. But if nobody has seen this, say you, how can they know it for a fact?