Robert Hooke showed the Royal Society microscopical observations of the liquor in a ram's testicles

July 27, 1679

Hooke's experiments here were following up on Leeuwenhoek's letter of 25 April to Grew about the vast number of sperm in a cod's milt. The second experiment concerned Denis Papin's "exhausting engine".


Birch, History, vol III, p. 497 17 July 1679 (O.S.) in London:

Mr. Hooke shewed two experiments: the first was the testicle of a lamb, which being dissolved, and the liquor contained in it examined in a microscope, it was found not to have any live animals, but to be exceedingly full of the small globules. Whether there had been any creatures in it, and were now dead, by reason that the lamb had been killed in the morning; or whether there were not as yet any living creatures in it, the lamb being not come to maturity for generation, could not be distinguished. But farther trial in order to this inquiry was desired to be made on a young lamb's stone, as soon as the creature should be killed.