While it is only with modern chemistry and toxicology that we have begun to understand the mechanisms by which poisons work, a remarkable amount was known about the effects, uses and treatments of poisoning, even in the relatively unscientific world of medieval Europe (Hallakarva, 1994).
The purveyors of medieval potions and poisons were apothecaries. They produced and sold preparations for a multitude of uses, and it was well known that many of these could be put to less beneficial purposes than those for which they were intended. In Chaucer’s Canterbury Tales (ca.1343-1400), the Pardoner tells of a would-be murderer buying some poison on the pretence of needing it to deal with a rat infestation:
"And forth he goes – no longer he would tarry –
Into the town unto a ‘pothecary
And prayed him that he woulde sell
Some poison, that he might his rattes quell…
The ‘pothecary answered: "And thou shalt have
A thing that, all so God my soule save,
In all this world there is no creature
That ate or drunk has of this confiture
Not but the montance of a corn of wheat
That he ne shall his life anon forlete.
Yea, starve he shall, and that in lesse while
Than thou wilt go a pace but not a mile
The poison is so strong and violent."
Poisoning was a popular subject of fiction, as it has been in every age, but there were also academic texts published on the subject. These were often written by monks; monasteries being the main seats of learning in a largely illiterate population.
One example is "The Book of Venoms", which was written by Magister Santes de Ardoynis in 1424. This was a reasonably comprehensive account of the poisons known at the time, their effects and the best ways that they could be treated.
Many of the poisons used more recently; arsenic, cyanide, strychnine, opium, atropine, aconite and heavy metals, were described in these treatises. They were often referred to by several different names, or as the plant from which they have more recently been purified, but were usually described with great accuracy and with surprisingly little variation from modern toxicological texts. The majority of these treatises were based on writings from the ancient world, as was a great deal of medieval medicine and scholarship in general.
It is unlikely that these academic documents would have been available, or comprehensible to the public. However, there was also a great deal of lay poison-lore:
The high profile of poisons and poisoners, the fact that they worked unseen, and their association with witchcraft resulted in a level of paranoia in some sections of the population. This may in fact have been justified, as, with poisons readily available and no science of forensics or toxicology to provide convicting evidence, poisoning seems to have been relatively widespread.
Methods of defence against poisons became very popular, and while some writings on antidotes, treatments and methods of avoiding poisons were quite reliable, there were also a great many creative, and entirely inaccurate, suggestions. Drinking vessels made from "unicorn’s horn", rhino horn, or various gemstones were alleged to neutralise any poison contained in them. These materials, already valuable, became even more sought after, and could raise a huge price.
No doubt canny salesman would have taken advantage of this, and helped their cause by persuading wealthy customers that poisoners were everywhere, and that the only way they could save themselves was to buy the gemstone, potion or whatever other charm the salesman was offering.
More easily obtainable anti-poison charms were also used, such as toadstones: calcified stones from the stomach’s of toads. An inventory of the possessions of Mary Queen of Scot’s in 1586 listed "a little silver bottle containing a stone medicinable against poison".
Some religious artefacts, such as amulets and talismans, were also thought to be protective against poisoning. These were largely introduced by Jews, a race with a mixed reputation with respect to poisoning. Despite their association with protective charms, the scheming Jewish poisoner was a popular figure of fear and hate in the xenophobic Christian populations of medieval Europe, and is one that has persisted even into the twentieth century. The large number of Jewish doctors in Germany and Austria during Nazi rule and the unfounded claims that they were systematically poisoning the Christian population, contributed to the anti-Semitic paranoia and hatred that culminated in the holocaust.
An examination of poisoning in the middle ages illustrates the way in which scientific knowledge became much more a part of the public consciousness over the next few hundred years; in the course of the renaissance and the industrial revolution. While reliable information did exist on poisoning and its treatment, it was largely restricted to the tiny educated minority, while the public at large was left to use second or third hand versions to create their own ideas and opinions.
This discrepancy, with respect both to poisoning and to scientific knowledge in general, has been greatly reduced by the huge increases in levels of literacy, and by the enormous improvements in communication and in education.