United States or San Marino ? Vote for the TOP Country of the Week !
The air is drawn into the lungs by the action of the diaphragm, a great, strong, flat, sheet-like muscle, stretched across the chest, separating the chest-box from the abdomen. The diaphragm's action is almost as automatic as that of the heart, although it may be transformed into a semi-voluntary muscle by an effort of the will.
Word Of The Day