Breathing

The act of respiration. The organs concerned in breathing are the nostrils, the wind¬ pipe and the lungs. The wind-pipe is a stout tube, divided below into two tubes, one of which goes to the right and the other to the left lung. When the ribs are elevated and the diaphragm is depre ed, there is a tendency to produce a vacuum between the lungs and the wall-chest. The air forces its way into the air-pa ages of the lungs, and expands the lung ti ue so that it fills the enlarged space within the chest. This is in¬ spiration. When the ribs and diaphragm return to their pa ive condition, the pre ure of the air compelled to breathe the same air twice but in