We do not put the whole body of the viper into theriac, but cut off the heads and tails and use the rest of the body in the mixture. We do not do this capriciously, nor without reason, but because the head contains the worst of the bodily fluids, the poison itself, and so we try to cut them off so that the drug should have less of their power, since the nature of these heads has a certain power of turning things to poison just as sperm is created by changes occurring in the testicles, and milk in the breast. The female viper has a head more suited for destruction than any other creature. For they say it opens its mouth to receive the male’s semen, and then when it has got it to cut off his head; and this is the method of their foul intercourse. Then the creatures born from the sperm by a sort of natural revenge eat through the mother’s stomach and emerge into the open and so kill the mother to avenge the father. So the great Nicander writes elegantly in his poetry, and these are his words:

“Do not be at the crossroads when the dusky viper escaping her bite is enraged by the blow of the sooty-coloured she-viper when, as the male mounts her, leaping and fastening her furious bite in him, she cuts off her husband’s head. But the little snakes which are born follow up the outrage against their father when they orphan themselves by breaking out of their mother’s slender body.”