In Search Of A Son Part 25

"There is n.o.body living who really understands this matter very well, for it is an extremely obscure, though very important, subject," replied Monsieur Roger. "But, to resume our explanation. Besides oxygen and nitrogen, there is also in the air a little carbonic acid and vapor. The carbonic acid will bring us back to the point from which we started,--the phenomenon of breathing. Carbonic acid is a gas formed by oxygen and carbon. The carbon is a body which is found under a large variety of forms. It has two or more varieties,--it is either pure or mixed with impurities. Its varieties can be united in two groups. The first group comprises the diamond and graphite, or plumbago, which are natural carbon. The second group comprises coal, charcoal, and the soot of a chimney, which we may call, for convenience, artificial carbon.

When oxygen finds itself in contact with carbonaceous matter,--that is to say, with matter that contains carbon,--and when the surrounding temperature has reached the proper degree of heat, carbonic acid begins to be formed. In the oven and the furnace, coal and charcoal mingle with the oxygen of the air and give the necessary heat; but it is first necessary that by the aid of a match, paper, and kindling-wood you should have furnished the temperature at which oxygen can join with the carbon in order to burn it. That is what we may call an active or a live combustion; but there can also be a slow combustion of carbon,--a combustion without flame, and still giving out heat. It is this combustion which goes on in our body by means of respiration."

"Ah, now we have come around to it!" cried Miette. "That is the very thing I was inquiring about."

"Well, now that we have come around to it," answered Monsieur Roger, "tell me what I began to say to you on the subject of respiration."

"That is not very difficult," answered Miette, in her quiet manner. "You told us that we swallowed oxygen and gave out carbonic acid; and you also said, 'Whence comes this carbonic acid? From combustion.' That is why I said, just now, 'We have come around to it.'"

"Very good,--very good, indeed, only we do not _swallow_ oxygen, but we _inhale_ it," said Monsieur Dalize, charmed with the cleverness of his little girl.

"What, then, is the cause of this production of carbonic acid?"

continued Monsieur Roger. "You don't know? Well, I am going to tell you.

The oxygen of the air which we breathe arrives into our lungs and finds itself in contact with the carbon in the black or venous blood. The carbon contained here joins with the oxygen, and forms the carbonic acid which we breathe out. This is a real, a slow combustion which takes place not only in our lungs,--as I said at first, in order not to make the explanation too difficult,--but also in all the different portions of our body. The air composed of oxygen and nitrogen--for the nitrogen enters naturally with the oxygen--penetrates into the pulmonary cells, spreads itself through the blood, and is borne through the numberless little capillary vessels. It is in these little vessels that combustion takes place,--that is to say, that the oxygen unites with the carbon and that carbonic acid is formed. This carbonic acid circulates, dissolved in the blood, until it can escape out of it. It is in the lungs that it finds liberty. When it arrives there it escapes from the blood, is exhaled, and is at once replaced by the new oxygen and the new nitrogen which arrive from outside. The nitrogen absorbed in aspiration at the same time as the oxygen is found to be of very much the same quant.i.ty when it goes out. There has therefore been no appreciable absorption of nitrogen. Now, this slow combustion causes the heat of our body; in fact, what is called the animal-heat is due to the caloric set free at the moment when the oxygen is converted into carbonic acid, in the same way as in all combustion of carbon. In conclusion, I will remind you that our digestion is exercised on two sorts of food,--nitrogenous food and carbonaceous food. Nitrogenous food--like fibrin, which is the chief substance in flesh; alb.u.men, which is the princ.i.p.al substance of the egg; caseine, the princ.i.p.al substance of milk; legumine, of peas and beans--is a.s.similated in our organs, which they regenerate, which they rebuild continually. Carbonaceous foods--like the starch of the potato, of sugar, alcohol, oils, and the fat of animals--do not a.s.similate; they do not increase at all the substance of our muscles or the solidity of our bones. It is they which are burned and which aid in burning those waste materials of the venous blood of which I have already spoken.

Still, many starchy foods do contain some nutritive principles, but in very small quant.i.ty. You will understand how little when you know that you would have to eat about fifteen pounds of potatoes to give your body the force that would be given it by a single pound of beef."

"Oh," said Miette, "I don't like beef; but fifteen pounds of potatoes,--I would care still less to eat so much at once."

"All the less that they would fatten you perceptibly," replied Monsieur Roger; "in fact, it is the carbonaceous foods which fatten. If they are introduced into the body in too great a quant.i.ty, they do not find enough oxygen to burn them, and they are deposited in the adipose or fatty tissue, where they will be useless and often harmful. You see how indispensable oxygen is to human life, and you now understand that if respiration does not go on with regularity, if the oxygen of your room should become exhausted, if the lungs were filled with carbonic acid produced by the combustion of fuel outside the body, there would follow at first a great deal of difficulty in breathing, then fainting, torpor, and, finally, asphyxia."

These last words, p.r.o.nounced by Monsieur Roger with much emotion, brought before them a remembrance so recent and so terrible that all remained silent and thoughtful. It was Miss Miette who first broke the spell by asking a new question of her friend Roger. Asphyxia had recalled to her the fire. Then she had thought of the manner of extinguishing fire, and she said, all of a sudden, her idea translating itself upon her lips almost without consciousness,--

"Why does water extinguish fire?"

Monsieur Roger, drawn out of his thoughts by this question, raised his head, looked at Miette, and said to her,--

"In the first place, do you know what water is?"

"No; but you were going to tell me."

"All right. The celebrated Lavoisier, after having shown that air is not a simple body, but that it is composed of two gases, next turned his attention to the study of water, which was also, up to that time, considered to be an element; that is, a simple body. He studied it so skilfully that he succeeded in showing that water was formed by the combination of two gases."

"Of two gases!--water?" cried Miette.

"Certainly, of two gases. One of these gases is oxygen, which we have already spoken of, and the other is hydrogen."

"Which we are going to speak of," added Miette.

"Of course," answered Monsieur Roger, "since you wish it. But it was not Lavoisier, however, who first discovered hydrogen. This gas had been discovered before his time by the chemists Paracelsus and Boyle, who had found out that in placing iron or zinc in contact with an acid called sulphuric acid, there was disengaged an air "like a breath." This air "like a breath" is what we now call hydrogen. Lavoisier, with the a.s.sistance of the chemist Meusnier, proved that it was this gas which in combining with oxygen formed water. In order to do this he blew a current of hydrogen into a retort filled with oxygen. As this hydrogen penetrated into the retort, he set fire to it by means of electric sparks. Two stop-c.o.c.ks regulated the proper proportions of the oxygen and the hydrogen in the retort. When the combustion took place, they saw water form in drops upon the sides of the retort and unite at the bottom. Water was therefore the product of the combination of hydrogen with oxygen. The following anecdote is told in regard to this combination. A chemist of the last century, who was fond of flattery, was engaged to give some lessons to a young prince of the blood royal.

When he came to explain the composition of water, he prepared before his scholar the necessary apparatus for making the combination of hydrogen and oxygen, and, at the moment when he was about to send the electric spark into the retort, he said, bowing his head,--

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"'If it please your Royal Highness, this hydrogen and oxygen are about to have the honor of combining before you.'

"I don't know if the hydrogen and the oxygen were aware of the honor which was being done them; but certainly they combined with no more manners than if their spectator was an ordinary boy. Now, I may add, you must not confound combinations with mixtures; thus, air is a mixture of oxygen and nitrogen, while water is a combination of hydrogen and oxygen. This combination is a union of the molecules of the two gases which produces a composite body formed of new molecules. These new molecules are water. Now, this last word recalls to me Miette's question."

"Yes," said the latter: "why does water put out fire?"

"There are two reasons for this phenomenon," said Monsieur Roger: "the first is that water thrown upon the fire forms around the matter in combustion a thick cloud, or vapor, which prevents the air from reaching it. The wood, which was burning--that is to say, which was mingling with the oxygen of the air--finds its communication intercepted. The humid vapor has interposed between the carbon of the wood and the oxygen of the air; therefore, the combustion is forced to stop. Further, water falling upon the fire is transformed, as you very well know, into vapor, or steam. Now, this conversion into vapor necessitates the taking up of a certain quant.i.ty of heat. This heat is taken away from the body which is being burned, and that body is thus made much cooler; the combustion therefore becomes less active, and the fire is at last extinguished."

"Very good," said Miette; "but still another question, and I will let you alone."

"You promise?"

"Yes."

"Well, then, what is your last question?"

"Why is a candle put out by blowing on it, and why do they light a fire by doing the same thing?"

"In these two cases there are two very different actions," replied Monsieur Roger: "in the first there is a mechanical action, and in the second a chemical action. In blowing upon a candle the violence of the air which you send out of your mouth detaches a flame which holds on only to the wick. The burning particles of this wick are blown away, and consequently the combustion is stopped. But the case is very different when you blow with a bellows or with your mouth upon the fire in the stove. There the substance in combustion, whether wood or coal, is a ma.s.s large enough to resist the violence of the current of air you throw in, and it profits from the air which you send to it so abundantly, by taking the oxygen which it contains and burning up still more briskly.

"Now, that is the answer to your last question; and I must beg you to remember your promise, and ask me no more hard questions to-night."

"Yes, friend Roger," said Miette, "I will leave you alone; you may go to sleep."

"And it will be a well-earned sleep," added Madame Dalize, with the a.s.sent of every one.

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CHAPTER XXVII.

PAUL OR GEORGE?

At the end of this long talk every one rose. Monsieur and Madame Dalize, with Monsieur Roger and Albert, walked towards the chateau. Paul Solange, silent and motionless, followed them with his eyes. When Monsieur Roger reached the step, he turned and made a friendly gesture to Paul, who responded by a bow. His eyes, in resting on Monsieur Roger, had an affectionate, softened, and respectful look. Miette saw it, and was struck by it. She approached, pa.s.sed her arm in Paul's, and said, softly,--

"You love him very much,--Monsieur Roger?"

"Yes," answered Paul, with surprise.

"You love him very, very much?"

"Yes."

"And he too loves you very well. I can see that. But do you love him as much as if he----?"

And Miette paused, embarra.s.sed a little, feeling that what she was going to say was very important; still, being certain that she was right, she continued:

"As much as if he was--your papa?"

Paul started.