“Just as the supposed number may differ from the true number by fully 100, 150, or even 200 in a flock of 600 sheep, so may I be even more out of my reckoning in the case of these very little animalcules.”

There was discover’d by me a fifth sort, which had near the thickness of the former, but they were almost twice as long. The first time bacteria were observed.

The 4th sort of creatures… which moved through the 3 former sorts, were incredibly small, and so small in my eye that I judged, that if 100 of them lay [stretched out] one by another, they would not equal the length of a grain of course Sand; and according to this estimate.

I make the proportion of one of these small Water-creatures to a Cheese-mite, to be like that of a Bee to a Horse:

Among other things, I saw in the body of one of these animalcules a bright and round corpuscle, placed near the head, and in which a very wonderful swift motion was to be seen, consisting of an alternate extension and contraction.

[M]y work, which I’ve done for a long time, was not pursued in order to gain the praise I now enjoy, but chiefly from a craving after knowledge, which I notice resides in me more than in most other men.

In it, that sometimes more than a thousand were moving about in an amount of material the size of a grain of sand…

Whenever I found something remarkable, I have thought it my duty to put down my discovery on paper, so that all ingenious people be informed thereof.

Man has always to be busy with his thoughts if anything is to be accomplished.

In the year 1657 I discovered very small living creatures in rain water.

And I judge that some of these little creatures were above a thousand times smaller than the smallest ones I have ever yet seen, upon the rind of cheese, in wheaten flour, mould, and the like.

I’ve spent more time than many will believe [making microscopic observations], but I’ve done them with joy, and I’ve taken no notice those who have said why take so much trouble and what good is it?

The 31th of May, I perceived in the same water more of those Animals, as also some that were somewhat bigger.

And therewithal, whenever I found out anything remarkable, I have thought it my duty to put down my discovery on paper, so that all ingenious people might be informed thereof.

This particle I concluded to be the heart.

For, the circumference of one of these little Animals in water, is not so big as the thickness of a hair in a Cheese-mite.

And I imagine, that [ten hundred thousand] of these little Creatures do not equal an ordinary grain of Sand in bigness: And comparing them with a Cheese-mite (which may be seen to move with the naked eye)

I gave my beauty and my youth to men. I am going to give my wisdom and experience to animals.

Until one has loved an animal, a part of one’s soul remains unawakened.

The eagle never lost so much time as when he submitted to learn of the crow

If I could do anything about the way people behave towards each other, I would, but since I can’t, I’ll stick to animals.

The lamb misused breeds public strife And yet forgives the butcher’s knife.

There’s a lot of us out here that are birds, man. We all need to just fly.

The misery of keeping a dog is his dying so soon. But, to be sure, if he lived for fifty years and then died, what would become of me?

The tigers of wrath are wiser than the horses of instruction.