For, as you know, venous blood is still impure and dirty blood.

Before it can be really alive it must pass through the veins to the right side of the heart, flow through into the upper chamber, then through another door or valve into the lower, where it is pumped out into the lungs.

If these lungs are, as they should be, full of pure air, each corpuscle is so charged with oxygen, that the last speck of impurity is burned up, and it goes dancing and bounding on its way.

That is what health means: perfect food made into perfect blood, and giving that sense of strength and exhilaration that we none of us know half as much about as we should.

We get it sometimes on mountain-tops in clear autumn days when the air is like wine; but God meant it to be our daily portion, and this very despised knowledge of cookery is to bring it about.