> And that’s what the birds have with their lungs: an in point and an out point. They also have air sacs and hollow spaces in their bones. When they breathe in, half of the good air (with oxygen) goes into these hollow spaces, and the other half goes into their lungs through the rear entrance. When they breathe out, the good air that has been stored in the hollow places now also goes into their lungs through that rear entrance, and the bad air (carbon dioxide and water vapor) is pushed out the front exit.
Isn't "front exit" the "front entrance"? They don't have two mouths. I don't understand how this improves things.
Isn't "front exit" the "front entrance"? They don't have two mouths. I don't understand how this improves things.