This reminds me that we are on the road to explain respiration, which I had almost forgotten in lifting up this corner of the veil behind which Nature hides her most valuable secrets from the idle and ignorant.
It is oxygen then, which the blood carries off triumphantly from his interview with the air in the cells of the lungs; and, by the way, it is, thanks to this oxygen that it returns from the lungs to the heart, and so from the heart to the organs, with that beautiful rosy tint which distinguishes arterial from venous blood.
Now the blood gives out this oxygen on its road every time it performs the journey, and the perpetual course it performs from the lungs to the organs, and from the organs to the lungs, has for its chief object the perpetual renovation of this previous provision, which is as perpetually consumed.
Do you ask of what use it is? Does the blood leave it at random in our organs, and is it one of the materials with which our steward is constantly providing the little workmen of the body for their various constructions?
No, my dear child. The proverb "One cannot live upon air," is a very true one, although it is equally true that we cannot live without air. Air does not nourish our organs; on the contrary, it consumes them, and what we eat, serves to supply in precisely the same proportion its insatiable appetite. When we leave off eating, from whatever cause, the air does not leave off too. He goes on always just the same, and that is the reason why people who are starved to death are so thin. (The air has consumed the vital parts.)
You did not expect this; but now prepare yourself to go on from one surprise to another. To begin with, I shall have to stop here and explain to you before we go any further—can you guess what? Nay, I am sure you cannot; FIRE.
There is not much connection, you will say, between fire and breathing.
But there you are mistaken. It is precisely the same thing, as I will prove to you next time.