CHAPTER X
BREATHING, HEAT, AND CLOTHING
100. The lungs.—Our food becomes blood and feeds the cells of our body, but we grow only a little heavier. What becomes of the food?
The air tubes and lung.
a larynx or voice box.
b trachea or windpipe.
d air sacs, each like a tiny frog's lung.
Besides food, air is always getting into our bodies. In breathing, air passes through the nose into a tube in the neck. This tube is called the windpipe. You can feel it as a pile of hard rings in the front part of the neck. The windpipe divides into many branches. At the end of its smallest branches are little bags or sacs. The branches and the sacs make the two lungs. So a lung is a soft and spongy piece of flesh, and can be blown up like a rubber bag. A frog's lung is a single, thin bag, about half an inch across it. Each little sac of a man's lung is like a tiny frog's lung.
A frog's lung (×4).