22. As we saw, however, that the liver has especial need of the co-operation of heat for the conversion of the fluids into blood, while this organ is in position distant from the heart (for it would, I imagine, have been impossible that, being one principle or root of the vital power, it should not be hampered by vicinity with another such principle), in order that the system may suffer no injury by the distance at which the heat-giving substance is placed, a muscular passage (and this, by those skilled in such matters, is called the artery) receives the heated air from the heart and conveys it to the liver, making its opening there somewhere beside the point at which the fluids enter, and, as it warms the moist substance by its heat, blends with the liquid something akin to fire, and makes the blood appear red with the fiery tint it produces.