Timaeus

And inasmuch as one part thereof is better, and one worse, they built a division within the cavity of the thorax— as if to fence off two separate chambers, for men and for women—by placing the midriff between them as a screen. That part of the soul, then, which partakes of courage and spirit, since it is a lover of victory, they planted more near to the head, between the midriff and the neck, in order that it might hearken to the reason, and, in conjunction therewith, might forcibly subdue the tribe of the desires whensoever they should utterly refuse to yield willing obedience to the word of command from the citadel of reason. And the heart, which is the junction of the veins and the fount of the blood which circulates vigorously through all the limbs, they appointed to be the chamber of the bodyguard, to the end that when the heat of the passion boils up, as soon as reason passes the word round that some unjust action is being done which affects them, either from without or possibly even from the interior desires, every organ of sense in the body might quickly perceive through all the channels both the injunctions and the threats and in all ways obey and follow them, thus allowing their best part to be the leader of them all. And as a means of relief for the leaping of the heart, in times when dangers are expected and passion is excited—since they knew that all such swelling of the passionate parts would arise from the action of fire,—they contrived and implanted the form of the lungs. This is, in the first place, soft and bloodless; and, moreover, it contains within it perforated cavities like those of a sponge, so that, when it receives the breath and the drink, it might have a cooling effect and furnish relief and comfort in the burning heat. To this end they drew the channels of the windpipe to the lungs, and placed the lungs as a kind of padding round the heart, in order that, when the passion therein should be at its height, by leaping upon a yielding substance and becoming cool, the heart might suffer less and thereby be enabled the more to be subservient to the reason in time of passion. And all that part of the Soul which is subject to appetites for foods and drinks, and all the other wants that are due to the nature of the body, they planted in the parts midway between the midriff and the boundary at the navel, fashioning as it were a manger in all this region for the feeding of the body; and there they tied up this part of the Soul, as though it were a creature which, though savage, they must necessarily keep joined to the rest and feed, if the mortal stock were to exist at all.