Health lectures for the people : third series, delivered in Edinburgh during the winter of 1882-83.
- Date:
- 1883
Licence: Public Domain Mark
Credit: Health lectures for the people : third series, delivered in Edinburgh during the winter of 1882-83. Source: Wellcome Collection.
Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.
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![of it into his chest every time that he breathes. You will ask— What is the use of the nitrogen ] The answer is, that the oxygen would be too strong for us; we should burn too quickly, just like the candle, and we should perish. And therefore the use of the nitrogen in the atmospheric air is simply to dilute the oxygen and to enable us to breathe it steadily, readily, and profitably. But there is also carbonic acid in the air, four parts in ten thousand. That is so universally diffused through the air that nowhere do we find the air without it. There is always some of it present, but in very minute quantity, as you see. Where does that carbonic acid come from 1 It comes from the breathing of every animal upon the surface of the globe, from everything that is burning upon the face of the globe, whether it be a small taper or a burning mountain like Etna or Vesuvius. Both in the act of burning in the case of the taper, and in the act of breathing in the case of the animal, carbonic acid is formed in quantity, and the air therefore becomes contaminated with it. And if, there- fore, we have no renewal of the air; if we have not a proper supply of fresh air furnished to us for our breathing, we should go out just as the candle does in a jar containing carbonic acid. Now, you may say— Oh, that is just our friend the nitrogen back again ! No ; it is something very different, as you will see when I mix with it some clear lime water. The mixture, you see, has become quite turbid, and that is because the acid has joined with the lime to form this substance. The same effect is produced when I blow into a jar of lime water, and therefore you see that we are always pouring out a quantity of this gas from our lungs. Now, there is a marked difference, between this gas and the nitrogen as regards its properties. The nitrogen has little or no properties except of a negative kind. It won't sup- port burning or breathing, but it won't poison in itself; that is to say, it is not absolutely noxious in itself. But it is very different with the carbonic acid. This is a poisonous gas, has deleterious pro- perties in itself, is capable, in fact, as a poison, of extinguishing life ; and all of you must have heard often enough of the disastrous consequences that follow from breathing carbonic acid in very large](https://iiif.wellcomecollection.org/image/b21450729_0017.jp2/full/800%2C/0/default.jpg)
