Plants take in carbonic-acid gas through their leaves, and send the oxygen back into the air ready for us to use again.
This is carbonic-acid gas, which is a poison and will destroy life.
There are two reasons then why we breathe: (a) to obtain oxygen; (b) to get rid of carbonic-acid gas.
Here it combines with the carbonic-acid gas taken from the air.
The "Valley of Death," in the island of Java, is simply the crater of an extinct volcano, filled with carbonic-acid gas.
Then, after due consideration, it was decided to make the test with carbonic-acid gas instead.
What would have escaped up a chimney as carbonic-acid gas is confined here as a solid, and fire can yet liberate it.
At the first inception of the idea, it seemed that carbonic-acid gas would be the motive power best adapted for short flights.
Thus in the insects oxygen and carbonic-acid gas are not carried by the blood but by special air-tubes.
There was a good deal of carbonic-acid gas on Jupiter, but that would hardly confuse our senses.