A man named Francois is hired out to find poisoners

In May 1712 Governor Arnoul de Vaucresson opened his report to the ministry in Paris with a long run of losses among enslaved people and livestock in Martinique, from illnesses so unusual that the owners could not explain them. Several owners had arrested their slaves, held them in irons on the plantations, extracted confessions and then sent them on to the king's prison. One case in that report concerns an enslaved man named Francois, who claimed particular skill in detecting poisons, spells and the people who used them. His owner, a Mr David, hired him out during the crisis and collected money from the neighbours for it. The court dropped the case against the accused for want of proof, rebuked the owners who had abused them, and made David return the money for tricking the public. Slaveholders were learning who to suspect, and how to look, from the enslaved themselves.

The Atlantic trade in Africans was already old before anyone published a description of how it worked. The first such information appeared in 1675, in the manual of commerce written by Savary and known as the Perfect Merchant, and compilers of dictionaries drew on that account for generations afterwards. In 1723 Savary's universal dictionary of commerce set out the justification repeated for the rest of the century. It is difficult, the entry conceded, to justify the trade in Negroes altogether, and then argued that these wretched slaves found their salvation in the loss of their liberty and in the Christian instruction given them. The order of operations is what matters. The practice came first, in the search for hands cheap enough to dig gold and grow sugar, tobacco and cotton, and the theory explaining why the people bought deserved their condition was assembled afterwards, once buyers in Europe began asking.

Francisco Buytrago was a knight of the Order of Christ and a cavalry officer stationed in Angola for twenty years across the 1710s and 1720s. He spent that time watching medical practitioners in Angola and the kingdom of Kongo and asking them questions, and from them and from enslaved informants he learned about a small yellow tree with thick bark that he was told was the finest counter poison anywhere in the world. He saw healers use it on a man badly swollen from evil spells, and reported that people also carried the bark to keep harm from reaching them at all. The tree was almost certainly Erythrophleum suaveolens, called nkasa by Kikongo speakers, whose bark made the ordeal drink given to test the innocence of the accused and also served as a fishing poison. Buytrago drew none of that. He understood the bark as a new instrument for casting out demons and wrote a manuscript recommending it for exorcisms.

The Constitution of the Archbishopric of Bahia, issued in 1707, addressed the overlap between sorcery and medical practice entirely in European terms. The church held that nobody could manipulate nature, or appear to, except through a demon and a pact with the Devil. Lay healing worried it for a related reason. Seeking a cure by unsanctioned means opened the door to superstitions that endangered the soul. So the law forbade anyone to perform cures without a licence and the archbishop's approval, and stressed that no layperson might expel demons from a human body. Nothing in it mentioned Africans, and the rule on jurisdiction sent sorcery cases to the Inquisition only when they amounted to open heresy. Meanwhile free and enslaved practitioners of African descent went on treating afflictions attributed to poisons and charms, using divination and spirit possession, and Europeans as well as Africans went on paying them for it.