Galen tries to find some satisfactory explanation of the strange properties which he believes exist in so many things. The attractive power of the magnet and of drugs suggests to him that nature in us is divine, as Homer says, and leads like to like and thus shows its divine virtues.[784] Galen rejects Epicurus’s explanation of the magnet’s attractive power.[785] It was that the atoms flowing off from both the magnet and iron fit one another so closely that the two substances are drawn together. Galen objects that this does not explain how a whole series of rings can be suspended in a row from a magnet. Galen’s teacher Pelops, who claimed to be able to tell the cause of everything, explained why ashes of river crabs are used for the bite of a mad dog as follows.[786] The crab is efficacious against hydrophobia because it is an aquatic animal. River crabs are better for this purpose than salt water crabs because salt dries up moisture. He also thought the ashes of crabs very potent in absorbing the venom. But this type of reasoning is unsatisfactory to Galen, who finds the best explanation of all such action in the peculiar property, or occult virtue, of the substance as a whole. Upon this subject[787] he proposes to write a separate treatise, and in the fragment _De substantia facultatum naturalium_ (περὶ οὐσίας τῶν φυσικῶν δυνάμεων) he again discusses the matter.[788] [Sidenote: Virtue of the flesh of vipers.] Among parts of animals Galen regarded the flesh of vipers as especially medicinal, particularly as an antidote to poisons. Of the following cures wrought by vipers’ flesh which Galen narrates[789] two were repeated without giving him credit by Aëtius of Amida in the sixth, and Bartholomew of England in the thirteenth century, and doubtless by other writers. When Galen was a youth in Asia, some reapers found a dead viper in their jug of wine and so were afraid to drink any of it. Instead they gave it to a man near by who suffered from the terrible skin disease elephantiasis and whom they thought it would be a mercy to put quietly out of his misery. He drank the wine but instead of dying recovered from his disease. A similarly unexpected cure was effected when a slave wife in Mysia tried to kill her husband by offering him a like drink. A third case was that of a patient whom Galen told of these two previous cures. After resorting to augury to learn if he too should try it and receiving a favorable response, the patient drank wine infected by venom with the result that his elephantiasis changed into leprosy, which Galen cured a little later with the usual drugs. A fourth man, while hunting vipers, was stung by one. Galen bled him, extracted black bile with a drug, and then made him eat the vipers which he had caught and which were prepared in oil like eels. A fifth man, warned by a dream, came from Thrace to Pergamum. Another dream instructed him both to drink, and to anoint himself with, a concoction of vipers.