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

Antonie van Leeuwenhoek

For my part, I would say that the male sperm and seeds of plants have been penetrated so far that there is nothing further to discover in this great secret, but I could err in my opinion.
ANTONIE VAN LEEUWENHOEK

Biology Discover Errors Greatness Myself Opinion Plant Science Secret
Man has always to be busy with his thoughts if anything is to be accomplished.
ANTONIE VAN LEEUWENHOEK

Accomplishment Busy Himself Man Thinking
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
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
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

Freedom Man Myself Slave Stay Teaching
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
Ten hundred thousand of them could not equal the dimensions of a grain of such course Sand.
ANTONIE VAN LEEUWENHOEK

Course Dimension Equal Grainm Such Hundred Thousand Sand Ten
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.
ANTONIE VAN LEEUWENHOEK

Big Cheese Circumstance Mite One Thickness Water
I have oft-times been besought, by divers gentlemen, to set down on paper what I have beheld through my newly invented microscopia, but I have generally declined.
ANTONIE VAN LEEUWENHOEK

Decline Invention Myself Paper Time
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
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 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 Consist Crystalline Diver Driven Endeavor Globulus Hand Humidity Know Length Round Small Taking Through Timer Water
The whole circumference of each of these streaks was about the thickness of a hair of one’s head. … all consisted of very small green globules joined together: and there were very many small green globules as well. [The earliest recorded observation of the common green alga Spyrogyra.]
ANTONIE VAN LEEUWENHOEK

Circumstance Consist Each Other Examining Globule Green Small Well Whole
[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.
ANTONIE VAN LEEUWENHOEK

Chiefly Crave Done Knowledge Men More Praise Pursue Time Work
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
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