Specific form or valence.
Poisons may also be classified according to the form of their species (forma specifica). Some prove fatal owing to the excessive preponderance of one quality, being excessively hot or cold or moist or dry. Others are deadly because their entire composition, the very form of their species, is fatal. Peter then gives an interesting definition of this “specific form.” “It is nothing else than the value or valence (meritum) which any object composed of the four elements acquires from the proportions of those elements existing in this compound and from the influence of the fixed stars which regard the species of inferior compounds.” Through the light of the stars streaming down in straight lines pyramids of astral force concentrate upon terrestrial objects,—the same doctrine of stellar rays, emanation, and multiplication of species that we have met already in Alkindi, Grosseteste, and Roger Bacon. Peter adds that this specific form of any compound is not easy to discover except as human experience gradually reveals it empirically, “because we do not know and we never shall know the quantities and the weights of the elements in the compounds.” That is to say, Peter sees the desirability but despairs of the possibility of any such discovery as that of atomic weights and valences, and consequently of a true science of chemistry. His despair is not surprising in view of the fact that medieval men were still trying to conduct their scientific researches upon the outworn Greek hypothesis of only four elements, earth, air, fire, and water, all of which are really compounds and indeed in the middle ages were not supposed to be ever found in their pure state. Desperation like Peter’s was needed before science could be induced to take a fresh start, and, like Arnald of Villanova, he is to be given credit for an approach to the chemical conception of valence.
An allusion to alchemy.
With the subject of alchemy, it may be remarked in passing, Peter appears to have had little to do, and not even any spurious treatises on the subject are extant under his name, as they are in the cases of Albertus Magnus, Thomas Aquinas, Roger Bacon, Arnald of Villanova, and Raymond Lull. Colle,[2851] however, noted a passage in the Conciliator[2852] where Peter speaks of two friends of his who had told him that they had succeeded “by the art of decoction” in making silver which was true to every examination but from which they had not profited much openly.
Mineral, vegetable, and animal poisons.
In his second chapter Peter discusses various mineral, vegetable, and animal poisons under the caption, “Of each poison in particular” (De unoquoque veneno in speciali). Quicksilver made by the art of alchemy he declares a more deadly poison than natural mercury. He is either an early advocate of inoculation and homeopathy, or else is guilty of silly reasoning based upon sympathetic magic, when he states that the magnet taken internally produces melancholy and lunacy and that doctors employ it with other medicines to cure melancholy. Incidentally he mentions two kinds of magnet, one which attracts iron toward the north pole, another which draws human flesh toward the south pole. Vegetable poisons may be the juices of herbs, the fruit of trees, or seeds. Some animals have poison in their brains; some, in their tails; some, in the blood; some, in the saliva and spittle; some, in the gall; and some, in their entire bodies.
How poison takes effect.
The question, how poison takes effect upon the human body, occasions Peter considerable difficulty, since he is unwilling to admit either that the heart naturally attracts poison or that poison runs naturally to the heart. Avicenna says that a man with a hot heart offers the best resistance to poison, but Peter adds that much depends upon the human soul and the constellations. He notes that the action of poison is very similar to that of medicine and thinks that the art of medicine was suggested by the action of poisons. Incidentally he repeats from his authorities statements that there are trees whose shade is poisonous to sleep in or to bathe beneath, and that a man was killed by the vapor from wood cut near the caverns of serpents which was used as fuel in heating his bath. He also repeats the tale of Socrates and the dragon.[2853]
Safeguards against poison.
The fourth chapter is concerned with safeguards against poison, which often take the form of amulets and charms and are, if anything, even closer akin to magic than the poisons themselves. There are the horns of a serpent which sweat at the advent of certain poisons but not of others. There is the gem that ceases to gleam in the presence of poison. There is the stone which Alexander wore in his belt until a jealous snake stole it while he was bathing in the Euphrates. There is the following image recommended in the book of the Persian kings—possibly the Kiranides. Engrave the gem Ematites with a kneeling man girded by a serpent whose head he holds in his right hand and tail in the left.[2854] Set this stone in a gold ring and under the gem place a dried root of serpentaria. Either Peter or the author of the book of the Persian kings affirms that he wears such a ring and has been preserved from poisoning by it. An emerald is another good safeguard against poison. Peter perhaps has a confused recollection of a story told by Albertus Magnus[2855] when he adds that it has been proved that a toad’s eyes will crack if it gazes at an emerald. There are seven herbs, namely: Ipericon, “which Achilles is said to have found in the Trojan army by the oracle of Apollo,” Vincetoxicum, Enula, Rafanus, Diptamus, Aristologia, and Lactucella, which will cure any poison. This virtue is not due to the elements composing them but to the force of the seven planets. Peter’s antidotes are not all occult or talismanic. He also prescribes the more commonplace methods of a drink of butter and hot water to provoke vomiting, the use of a syringe to clear the intestines, the application of a relay of hot fowls to the wound, or the sucking of it “by the mouth of some slave or servant”—sclavi vel servi, an interesting bit of etymological evidence of the medieval transition from the Latin servus to the modern word “slave,” and for the derivation of the latter from the Slavs who were sold in southern and western Europe. Peter also mentions the famous terra sigillata which, he says, causes vomiting if there is any poison in the stomach. Kings and princes in the west[2856] take it with their meals as a safeguard, and it is called terra sigillata because stamped with the king’s seal. Now, however, the seals are no longer trustworthy and Peter cautions the pope against what may be offered him as terra sigillata.[2857] Over seventy brief chapters are next devoted to enumeration of the effects produced by as many poisons and how to remedy them. The poisons include the blood of a rubicund, choleric man, the bite of a fasting man, the gall of a leopard, and the salamander. Among the remedies are duck’s fat and pulverized mouse dung. The remedies operate against the poison either by “breaking its sharpness,” or “resolving its substance,” or “expelling it,” or “corrupting it and utterly taking away its virtue.”