Antonie van Leeuwenhoek

“If any person examines by the microscope that part towards the extremity of the spider's body from whence its thread proceeds, he will observe the spot to be, as it were, surrounded by five several protuberances or risings, each ending in a point and altogether forming a kind of enclosure.”

“No one can pretend to say that a fish is ever killed by heat, for many kinds of fish, in the middle of summer, and in the burning heat of the sun, do either play, as it were, on the surface of the water, or hide themselves under the leaves, weeds, or other substances at the bottom.”

“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.”

“We will admit that, out of the mud or sand which is found on the seashore or the beds of our rivers, at low water, shellfish or testaceous animals come forth, but it does not from thence by any means follow that they are produced without any regular course of generation.”

“Man comes not from an egg but from an animalcule that is found in male sperm.”

“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.”

“How inscrutable and incomprehensible are the hidden works of Nature!”

“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.”

“I now found that the spider cannot fix its thread to anything without imprinting the hind part of its body on the place, by which pressure it emits an incredible number of excessively small threads diverging in every direction from whence we may conclude that as soon as the threads are exposed to the air, they lose their viscosity or gluey quality.”

“In rain water, I observed a small red worm and two other kinds of very minute insects; of those of the larger size, I judged that 30,000 together would not equal a coarse sand.”

“I must confess... I don't know any tongue but the Nether-Dutch.”

“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.”

“If we now plainly perceive that the passage of the blood from the arteries into the veins of the tadpole is not performed in any other than those vessels, which are so minute as only to admit the passage of a single globule at a time, we may conclude that the same is performed in like manner in our own bodies and in those of other animals.”

“Please bear in mind that my observations and thoughts are the outcome of my own unaided impulse and curiosity alone; for, besides myself, in our town there be no philosophers who practice this art, so pray, take not amiss my poor pen and the liberty I here take in setting down my random notions.”

“When I have supped too heavily of an evening, I drink in the morning a large number of cups of coffee, and that as hot as I can drink it, so that the sweat breaks out on me, and if by so doing I can't restore my body, a whole apothecary's shop couldn't do much, and that is the only thing I have done for years when I have felt a fever.”

“Life lives on life - it is cruel, but it is God's will. And it is for our good, of course, because if there weren't little animals to eat up the young mussels, our canals would be choked by those shellfish, for each mother has more than a thousand young ones at a time!”

“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.”

“I have lately examined water, in which beaten pepper was steeped, and found two sorts of animals for shape, and each of those sorts to contain greater and smaller kinds: the greater I supposed the elder, the less the younger.”

“A man has always to be busy with his thoughts if anything is to be accomplished.”

“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.”