In this article I discuss a particular aspect of the Dutch reception of the ideas of René Descartes, namely the use of his Traité de l’homme by Henricus Regius. I analyze the use that Regius made of the theory of the movement of muscles, passions, hunger, and more generally of the neurophysiology expounded by Descartes in his book (not printed until 1662–1664). In my analysis, I reconstruct the internal evolution of Regius’s neurophysiology, I illustrate its sources beyond Descartes (i.e., Jean Fernel and Santorio Santorio), and I show that he was certainly acquainted with some of its contents as early as 1641 (when he used it with the mediation of Descartes), before relying on it—as variously discussed in secondary literature—in his Fundamenta physices (1646), when he appropriated from it without Descartes’s authorization.