Christiaan Huygens wrote to Leeuwenhoek about other places to see the circulation of blood

March 6, 1689

Huygens thanked Leeuwenhoek for his mangrove tree (wortelboom) and inquired about Leeuwenhoek’s observations of the circulation of the blood. Would it not, he speculated, be seen also in the wings of bats, feed of ducks, and ears of rats?


Oeuvres complètes vol. IX. Correspondence 1685-1690, p. 310, No 2532.