Henschen had been a pupil of Jean Bolland. From the time of his arrival in the city he was associated as a collaborator with Bolland, who was then preparing the first volumes of the Acta Sanctorum. Bolland had asked for an assistant, a request supported by the abbot of Liessies Abbey, Antoine de Wynghe. In 1635 Henschen was assigned to start work on the February saints, while Bolland gave himself to the preparing the material for January. It was Henschen who, by his commentary on the Acts of St. Amand, suggested to Bolland the course to follow, and gave to the work undertaken by his mentor its definitive form. After fourteen years of work, the two volumes for January were printed in Antwerp in 1643 and greeted with enthusiasm by scholars. Work on the January volume was done in two garrets where Bolland kept his papers and books. As climbing the steep steps began to prove difficult, he asked for and obtained the use of a vacant room on the second floor, which later became the Bollandist Museum. The three volumes for February were released in 1658, and was equally well received. In 1660, at Bolland's direction, Henschen and Daniel van Papenbroek journeyed to Rome collecting ancient documents for their studies along the way. They stayed in Rome for nine months and returned by way of France. The five or six copyists placed at their disposal were kept constantly busy during the nine months they were in Rome in transcribing manuscripts according to their directions, and this occupation was continued by them a long time after the Bollandists departure. Their stay at Paris extended over three months, every moment of which time they spent in transcribing and collating, besides enlisting the services of several copyists during the entire time. Upon their return, they learned that Bolland had died, at which point he and Papenbroek began to lead the project. He was the first librarian of the Museum Bollandianum at Antwerp. Henschen continued to work on the Acta Sanctorum up to the time of his death. In total Henschen collaborated on the volumes for January, February, March, and April, and on the first six volumes for May, that is on seventeen volumes of the Acta Sanctorum. Several of his posthumous commentaries appeared in the succeeding volumes. A list of some other works from his pen will be found in Augustin de Backer's Bibliothèque des escrivains de la Compagnie de Jésus. He died at Antwerp, aged 80, in 1681.
