In 1828 Guislain became head of the psychiatric hospitals of Ghent, for which he wrote a new internal regulation together with Petrus Josef Triest. It was the first of its type and stipulated how to handle the patients in a decent and therapeutically justified way.
Guislain's appointment as head of Ghent's psychiatric hospitals in 1828 led to the development of a trailblazing internal regulation, written in collaboration with Petrus Josef Triest. The resulting policy emphasized patient dignity and therapeutic effectiveness.