HOW AND WHY WE BREATHE Life is Shown by Breathing.

If you wanted to find out whether a little black bunch up in the branches of a tree were a bird or a cluster of leaves, or a brown blur in the stubble were a rabbit or a clod, the first thing you would probably look for would be to see whether it moved, and secondly, if you could get close enough without its moving away, whether it were breathing.

You would know perfectly well if you saw it breathing that it was alive, and that, if it were not breathing at all, it would probably be dead, or very nearly so.
Why is breathing so necessary to life that it lasts practically as long as life does, and when it stops, life stops too?
Animals can stop eating for days, or even weeks, and yet live, especially if they were fairly fat when they began to fast.

Indeed, some animals, like woodchucks, bears, and marmots, will go to sleep in the fall, and sleep right on through to spring without eating a mouthful.

But if any animal or bird is prevented from breathing for three minutes, it will die.
Short Storage Supply of Air.