Blood, too, is the moister part of flesh, being a kind of liquid flesh; and milk is the sweeter and finer part of blood. For whether it be the blood supplied to the fœtus, and sent through the navel of the mother, or whether it be the menses themselves shut out from their proper passage, and by a natural diffusion, bidden by the all-nourishing and creating God, proceed to the already swelling breasts, and by the heat of the spirits transmuted, [whether it be the one or the other] that is formed into food desirable for the babe, that which is changed is the blood. For of all the members, the breasts have the most sympathy with the womb. When there is parturition, the vessel by which blood was conveyed to the fœtus is cut off: there is an obstruction of the flow, and the blood receives an impulse towards the breasts; and on a considerable rush taking place, they are distended, and change the blood to milk in a manner analogous to the change of blood into pus in ulceration. Or if, on the other hand, the blood from the veins in the vicinity of the breasts, which have been opened in pregnancy, is poured into the natural hollows of the breasts; and the spirit discharged from the neighbouring arteries being mixed with it, the substance of the blood, still remaining pure, it becomes white by being agitated like a wave; and by an interruption such as this is changed by frothing it, like what takes place with the sea, which at the assaults of the winds, the poets say, “spits forth briny foam.” Yet still the essence is supplied by the blood. In this way also the rivers, borne on with rushing motion, and fretted by contact with the surrounding air, murmur forth foam. The moisture in our mouth, too, is whitened by the breath. What an absurdity[240] is it, then, not to acknowledge that the blood is converted into that very bright and white substance by the breath! The change it suffers is in quality, not in essence. You will certainly find nothing else more nourishing, or sweeter, or whiter than milk. In every respect, accordingly, it is like spiritual nourishment, which is sweet through grace, nourishing as life, bright as the day of Christ.