Concluded series of observations of rams' testicles

July 30, 1700

Based on what he had seen on Saturday and Tuesday, Leeuwenhoek apparently had to tell someone or, better yet, show them.


In Letter 135 of 1700-12-25 (AB 220), Leeuwenhoek wrote to Hans Sloane:

On the 30th of July, at seven o'clock in the morning, I again received the testicles of a young ram, which I was told was about the same age as the former one. Hereupon I sent a request to three gentlemen to come to my house towards nine o'clock, so that I might show them something curious.

The first thing I did before their eyes was to push or squeeze the male sperm out of the vas deferens of one of the said testicles, and after having placed it before the magnifying glass I handed one after the other the glass, in which they saw, along with me, an incredible number (as they said) of living little animals, which were swimming about like clouds.

After this I opened the seminal vessels at the bottom of the testicle, where the seminal vessels lie, in a circle and as it were bundled up, enclosed in a membrane, and the aforesaid gentlemen had to confess, along with me, that in these vessels the number of the living little animals forming the male sperm was no smaller than in the former case.

A note on the translation

Leeuwenhoek used the Dutch phrase iets bijsonders which in today's English might be "something special" and Alle de Brieven / Collected Letters translated as "curious" and Sewel translated as "singular".