Today is the birthday of Antonii van Leeuwenhoek, and in honor of his achievement Google made an animated Doodle (click on it to go to Google). Since Matthew is an expert on the man and his science, which forms a part of his book The Egg and Sperm Race (also called Generation), I asked him to write a few words about the honoree (below).
by Matthew Cobb
Antonii Leeuwenhoek (he adopted the aristocratic ‘van’ as a pretension later in life) was one of the great figures of 17th century discovery. He was a draper, not a scholar, and yet he was able to make two of the most amazing discoveries in the history of science. Like many other people in the 17th century Dutch republic (including the great philosopher Spinoza), Leeuwenhoek (roughly pronounced Lay-wen-hoak) made microscopes out of a tiny bead of glass.
The lens was then put into a rectangular metal frame, and the object to be looked at (an insect, or a fluid in a capillary tube) was put on a rod on one side of the lens. The Google doodle shows this quite well. He then had to hold the apparatus into the sunlight (candlelight would not do) to see what he could see. Single lens microscopes were much more powerful than the compound microscopes of the time.
Leeuwenhoek’s two great discoveries were made early in his career (he was introduced to the Royal Society by one of his neighbours, the Delft-based Reinier de Graff, in 1672). In 1674, de Graaf was trying to find out why pepper is hot, so he ground up some pepper corns in water and allowed the solution to move up a capillary tube. His idea was to see the structure of whatever it was in pepper that made it spicy. Instead, he observed bazillions of tiny ‘animacules’ – bacteria and protists – zipping about in the water. For some years, it was assumed that the tiny things were released from the peppercorns, and it was called the ‘pepper water’ experiment. Until someone did the obvious thing of leaving out the pepper… Micro-organisms are still called ‘infusoria’ after this principle of making an ‘infusion’.
Leeuwenhoek’s second, and astounding discovery was made in 1677, when following the suggestion of a medical student, called Ham, Leeuwenhoek looked at his semen (this had previously been suggested to him by the Secretary of the Royal Society, Henry Oldenburg, but Leeuwenhoek declined to take the step). The description of how he did the experiment, which eventually appeared *in Latin* (not English) in the Philosophical Transactions of the Royal Society is interesting:
He reassured “his Lordships” that he had not obtained the semen by any “sinful contrivance” but by “the excess which Nature provided me in my conjugal relations.” Think about that. He goes on to say that a mere “six heartbeats” after ejaculation, he found “a vast number of living animalcules” in his ejaculate (it is not recorded what his wife thought of this…). The Royal Society didn’t believe him, and in classic modern style sent him away to do more experiments. Eventually, they published his report in 1678.
Several points: firstly, Leeuwenhoek at first thought that the sperm he saw were simply parasites (and this is reflected in the name we still give them – spermatozoa, the animals that live in semen). Second, he thought the interesting bit of the ejaculate was some weird thready material that no one else has seen before or since. He eventually changed his mind on this. Finally, although it had been suggested 10 years earlier that women have eggs, and de Graaf had shown experimental support for this idea in 1672 in rabbits, the scientific world did not recognise that egg and sperm were complementary components of the future organism.
That did not happen until the 1840s, after a) it was realised that something was inherited (the word ‘heredity’ had no biological meaning before the 1820s) and b) it was realised that all organisms are composed of cells, and therefore that egg and sperm were both cells. Instead, for 140 years science was more or less divided into the ovists and the spermists. For the spermists, like Leeuwenhoek, the egg was either non-existent (as in mammals) or food for the sperm; for the ovists (most people) the sperm somehow ‘awoke’ the egg, like an electric shock, but played no equal role in producing offspring.
Leeuwenhoek was an extraordinary man who made remarkable contributions to our understanding of the world. If you want to know more about him, and the weird route ideas took to come to our current understanding, despite it looking so obvious in retrospect, you can pick up a good second-hand copy of my 2006 book Generation, for less than $4! (In the UK it was called The Egg and Sperm Race…)