When the oxygen comes in contact with the blood, it unites with the hemoglobin of the blood and is carried to every cell, tissue, muscle and organ, which it invigorates and strengthens, replacing the worn out cells and tissue by new materials which Nature converts to her use.

Arterial blood, properly exposed to the air, contains about 25 per cent of free oxygen.
Not only is every part vitalized by the oxygen, but the act of digestion depends materially upon a certain amount of oxygenation of the food, and this can be accomplished only by the oxygen in the blood coming in contact with the food and producing a certain form of combustion.

It is therefore necessary that a proper supply of oxygen be taken through the lungs.

This accounts for the fact that weak lungs and poor digestion are so often found together.

To grasp the full significance of this statement, one must remember that the entire body receives nourishment from the food assimilated, and that imperfect assimilation always means an imperfectly nourished body.