Agatha Christie\u2019s poison murders are fasci\u00adna\u00adting \u2013 because even today they seem frigh\u00adten\u00adingly plau\u00adsible. One key reason lies in her trai\u00adning. During the First World War, she initi\u00adally worked as a nurse, then in a hospital phar\u00admacy \u2013 and did so again during the Second World War. There she prepared medi\u00adcines, weighed out active ingre\u00addi\u00adents and learnt first-hand just how fine the line between treat\u00adment and poiso\u00adning can be.<\/p>\n
The British chemist Kathryn Harkup has examined this back\u00adground in greater detail. She shows that Christie did not usually invent her poisons, but instead drew on real medi\u00adcinal subs\u00adtances and incor\u00adpo\u00adrated their mecha\u00adnisms of action into her plots with asto\u00adnis\u00adhing accuracy.<\/p>\n
From the medi\u00adcine cabinet to the crime novel<\/b><\/p>\n
One example is provided by the Miss Marple story \u2018The Case of the Caret\u00adaker\u2019. The murder weapon is stro\u00adph\u00adan\u00adthin, a cardiac glyco\u00adside origi\u00adnally isolated from African arrow poisons. In thera\u00adpeutic doses, it increases the heart\u2019s contrac\u00adtile force; however, a high intra\u00adve\u00adnous dose can trigger severe arrhyth\u00admias, even leading to cardiac arrest. Because stro\u00adph\u00adan\u00adthin was poorly absorbed when taken orally, it usually had to be admi\u00adnis\u00adtered by injec\u00adtion \u2013 a detail Christie knew from her time working in a phar\u00admacy and which her villain deli\u00adbera\u00adtely exploits.<\/p>\n
She incor\u00adpo\u00adrates a similar trick in *The Choco\u00adlate Box*: there, the female culprit hides Trini\u00adtrin \u2013 that is, nitro\u00adgly\u00adce\u00adrine, a heart medi\u00adca\u00adtion \u2013 in choco\u00adlates. However, Christie\u2019s plan does not quite work out. Accor\u00adding to Harkup\u2019s calcu\u00adla\u00adtions, the described dose alone would hardly have been lethal. Alcohol might have inten\u00adsi\u00adfied the blood-pres\u00adsure-lowe\u00adring effect \u2013 though Christie leaves it open as to whether the victim actually drank any.<\/p>\n
But Agatha Christie also takes certain liberties<\/b><\/p>\n
Not every detail stands up to modern know\u00adledge. In *Death in the Clouds*, Christie uses the venom of the boomslang snake, but depicts the typical blee\u00adding symptoms as unrea\u00adli\u00adsti\u00adcally incon\u00adspi\u00adcuous. The rapid iden\u00adti\u00adfi\u00adca\u00adtion of the rare poison also seems implau\u00adsible from today\u2019s perspec\u00adtive. This does not detract from the suspense \u2013 one would have to be very well-informed indeed to prove that Christie made a mistake at all.<\/p>\n