This dislike is due to certain gases, consisting of impurities from the blood, the cells of the lungs, the throat, the nose, and, if the mouth is open, the teeth.

These are not only offensive and disagreeable to smell, but poisonous to breathe.
Then your breath is much warmer than the rest of the air.

In fact, on a very cold morning you may have tried to warm up your fingers by breathing on them; and you have also noticed that if a number of people are shut up in a room with doors and windows closed, it soon begins to feel hot as well as stuffy.

This heat, of course, is given off from the blood in the lungs and in the walls of the throat and nose, as the air passes in and out again.
When you stand at the window on a cold day, the glass just in front of your mouth clouds over, so that you can no longer see through it; and if you rub your finger across this cloud, it comes away wet.

Evidently, the air is moister than it was when you breathed it in; this moisture also has been given off from the blood in the lungs.
But what of the principal waste gas that the blood gives off in the lungs--the carbon "smoke," or carbon dioxid?
Can you see any trace of this in the breath?
No, you cannot, for the reason that this gas is like air, perfectly clear and transparent, and never turns to moisture at any ordinary temperature.