Sam then bound the foot up with strips of cloth torn from his clothing, and as he did so said: "Now I'll tell you both all about this so that you'll know what to do another time.

If you know only _what_ to do, you may forget; but if you know _why_, you'll remember.

The blood comes out from the heart to all parts of the body in arteries, and when it leaves the heart it is bright red, because it is clean and pure.

Your heart is a sort of force-pump, and every time it beats it forces the blood all over you.

The arteries fork and branch out in every direction, until they terminate in millions of little veins smaller than the finest hairs, and these running together make bigger veins, through which the blood is carried to the lungs.