He practised as a doctor first in Maenza and then in Scandriglia in the province of Rieti, part of the domain of Duke Giovanni Antonio Orsini. In the course of his medical work, van Heeck became involved in a strange dispute. He treated his patients, who were mostly poor, with great zeal, using simple herbal medicines. For this reason he came into conflict with the apothecary of Scandriglia, one Casolini Ranieri, who made his living selling medicines with exotic names, more magical than scientific. Ranieri conceived a firm hatred of the foreign doctor, whose work threatened to ruin his lucrative business. One night Ranieri positioned himself on the route where van Heeck habitually passed and attacked him while he was alone. Van Heeck fell from his horse but fended off his attacker with a sword. Still bleeding from his injuries, he was brought before the magistrate. Despite his plea of self-defense, he was imprisoned. The apothecary later died of his wounds, and van Heeck would have been left to rot in prison if he had not been released through the intervention of Prince Federico Cesi, who sent Francesco Stelluti to get him out of prison and then invited him to his house in Rome.Domenico Carutti, Breve storia dell'Accademia dei Lincei, Roma, Salviucci, 1883, p. 6. The period when Cesi, van Heeck and Stelluti lived together after van Heeck's release from prison was one of an intense exchange of ideas and the shaping of plans, which led to the idea of forming a mutual-instruction society.Stillman Drake, Essays on Galileo and the History and Philosophy of Science, University of Toronto Press, 1999 vol.1 p.131
