Theodore Craanen wrote Letter L-048 to Leeuwenhoek, some time in 1677, requesting that his relative Johan Ham be allowed to visit

This letter is known only by reference in other letters.

In this letter, Leiden professor Theodore Craanen writes to L., requesting that his relative Johan Ham be allowed to visit and see some of Leeuwenhoek’s demonstrations.

This is the only known letter addressed to Leeuwenhoek from Theodore Craanen (1620-1690), professor of medicine in Leiden, proponent of Cartesian theories, and frequent visitor to Leeuwenhoek’s home. Johan Ham (1651-after 1723) was a native of Arnhem and a medical student in Leiden. On Ham’s second visit, he brought a vial of semen in which he had observed little animals.

See Letter L-029 of 1676, in this volume, for Leeuwenhoek’s only letter to Craanen.