I have divers times examined the same matter (human semen) from a healthy man… not from a sick man… nor spoiled by keeping… for a long time and not liquefied after the lapse of some time… but immediately after ejaculation before six beats of the pulse had intervened; and I have seen so great a number of living animalcules… in it, that sometimes more than a thousand were moving about in an amount of material the size of a grain of sand… I saw this vast number of animalcules not all through the semen, but only in the liquid matter adhering to the thicker part.