Published Den Waaragtigen Omloop des Bloeds (On the True Circulation of Blood), Letter 65 (L-200)

September 15, 1688

Publication by Voorstad in Delft of Den Waaragtigen Omloop des Bloeds, On the True Circulation of Blood in Eels, which Leeuwenhoek considered his showcase experiment, the one he entertained visitors with. The letter was dated September 7, 1688, so first publication of the pamphlet, while dated only 1688, was between that date and 23 September 1688, when he sent a copy of it to Thevenot.