"Well," said Fred, "before you can understand the breathing of the frog, I must make you think about the way in which we and most of the animals around us breathe.
"You can feel the ribs, which, pass right round the upper part of your body. They form a sort of air- tight box, which we call the chest. The chest holds the lungs, and the lungs are the breathing organs.
"Our ribs are constantly rising and falling. You can feel them rise and fall, if you put your hand on your chest. When they rise they make the chest larger, and the lungs inside expand; when they fall they make it smaller, and squeeze the lungs together again. As the lungs expand air rushes in atthe mouth and nostrils to fill them, and when they are pressed together the air is driven out. All this goes on without any effort on our part, and this is the way webreathe. The great thing for us to remember is that the frog has no ribs, and cannot therefore breathe in this way.
