11. But as furthermore in those who have ceased to live, when the heat that is implanted in our nature is quenched, that which has become dead grows cold, we hence recognize the vital cause also in heat: for we must of necessity acknowledge that the living being subsists by the presence of that, which failing, the condition of death supervenes. And of such a force we understand the heart to be as it were the fountain-head and principle, as from it pipe-like passages, growing one from another in many ramifications, diffuse in the whole body the warm and fiery spirit.