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I’ve never taught one, because if I taught one, I’d have to teach others. I would give myself over to a slavery, whereas I want to stay a free man.

Antonie van Leeuwenhoek

Examining this water…I found floating therein divers earthy particles, and some green streaks, spirally wound serpent-wise.
ANTONIE VAN LEEUWENHOEK

Diver Earth Examine Float Found Green Particle Serpent Some Streak Water Wise Wound
My determination is not to remain stubbornly with my ideas, but I’ll leave them and go over to others as soon as I am shown plausible reasons which I can grasp.
ANTONIE VAN LEEUWENHOEK

Determination Ideas Leaving Myself Reason Stubborn
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.
ANTONIE VAN LEEUWENHOEK

Animal Difference Myself Number True
I saw this vast number of animalcules not all through the semen, but only in the liquid matter adhering to the thicker part.
ANTONIE VAN LEEUWENHOEK

Adhere Animalcule Liquid Matter Number Part Saw Semen Thicker Through Vast
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.
ANTONIE VAN LEEUWENHOEK

Alternative Among Anmalcule ContrAction Head Moorningm Consist Place Swift Thing
I observed certain animalcules, within whole bodies I saw so quick a motion as to exceed belief; they were about the size of a large grain of sand, and their bodies being transparent, that the internal motion could plainly be seen.
ANTONIE VAN LEEUWENHOEK

Animalclue Belief Body Certain Internal Land Motion Observe Quick Seen Size Transfer
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.
ANTONIE VAN LEEUWENHOEK

Discovery Down Duty Found Inform People Remarkable Something
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?
ANTONIE VAN LEEUWENHOEK

Believe Goodness Myself Observation Time Trouble
For my part, I hold it equally impossible for a small shellfish to be produced without generation as for a whale to have its origin from the mud.
ANTONIE VAN LEEUWENHOEK

Equality Hold Myself Origin Production Small
The 31th of May, I perceived in the same water more of those Animals, as also some that were somewhat bigger.
ANTONIE VAN LEEUWENHOEK

Also Animal Bigger May More Perceive Same Somewhat Water
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.
ANTONIE VAN LEEUWENHOEK

Bacteria Discover Fifth First Former Long Observe Sort Thickness Time Twice
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.
ANTONIE VAN LEEUWENHOEK

Creature Equal Eye Grain Hope Incredibly Judge Length Move Sand Small Sort Through
In the year 1657 I discovered very small living creatures in rain water.
ANTONIE VAN LEEUWENHOEK

Creature Discover Live Rain Small Water Year
I have divers times endeavoured to see and to know, what parts the Blood consists of; and at length I have observ’d, taking some Blood out of my own hand, that it consists of small round globuls driven through a Crystalline humidity or water.
ANTONIE VAN LEEUWENHOEK

Blood Drive Humidity See Talk Time Water
I have often endeavoured to view the circulation of the blood in terrestrial animals, but without success, by reason that no parts of their bodies were sufficiently transparent.
ANTONIE VAN LEEUWENHOEK

Animal Blood Body Enough Success View
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)
ANTONIE VAN LEEUWENHOEK

Biggest Cheese Eye Grain Hundred Imagine Move Naked Ordinary Sand Thousand