As an anatomist - as anybody - looking at the pages of Leonardo da Vinci's notebooks on display in the Queen's Gallery, Buckingham Palace in London, is a humbling and mind-bending experience.
My first reaction to the beautifully displayed pages, each sandwiched between two sheets of glass so you can view both sides, was the smallness of his notebook, not much larger than A5, in fact. But Leonardo certainly crammed a lot into that space.
Each page is covered in minutely observed details of anatomy, framed by copious notes in his tiny, spidery mirror-writing (because it was easier for a left hander, or perhaps - I like to think, anyway - because it would make it difficult for anyone else to read and steal his ideas).
I've seen these images so many times before: the two skulls, sectioned to show the cavities within; a man and woman fused in coitus; the muscles of the back, the arm, the leg; the extraordinary rust-tinted foetus curled up inside its cut-open womb, like a kernel inside a strange fruit. But previously, I'd only seen photos, reproductions. Here I was gripped by their originality, freshness, immediacy: marks made on paper, in metalpoint and pen and ink, 500 years ago. What they reveal is the understanding achieved through the observation of nature, completely undiminished by the passing of centuries and the accumulation of theory.
His mind is open to the facts as revealed to him, not through the writings of wise men but through direct observation. He looked into the body of a human and saw it for what it was: a complex, beautiful and strange piece of machinery. He may not have understood how it all worked but he knew that the answers lay in such observation.
Are we trapped by our own theory when we look at his work today? I think so. Scholars writing about his work have been effusive about his masterly knowledge of anatomy, but seem to relish spotting errors, as though this underlines the idea of scientific progress: Leo was good, but of course he's not as good as us, today.
Perhaps some of these "errors" originate in the eye of the beholder. Might a drawn connection between a uterus and a breast represents something else - a different type of communication? Without knowing about the "love hormone" oxytocin, perhaps he's suggesting a more subtle connection between uterus and breast.
There's an extraordinary page of legs: well-muscled legs, the bones of the pelvis and legs - apparently human in proportion but a bit horse-like in their shape. Perhaps Leonardo had mis-drawn a human pelvis, being more familiar with equine anatomy. But what if he was deliberately playing with the anatomy - to see if the elements of a horse's leg could be rearranged to stand like a human?
In a drawing of an old man's abdomen, the modern note suggests that Leonardo is wrong in showing paired vessels stretching up to the umbilicus: there should only be one umbilical artery on each side. But we know from other drawings that this man's liver was cirrhotic; we'd therefore expect that veins around the umbilicus - usually insignificant - had enlarged to provide a bypass for blood around the hardened liver.
Perhaps I'm an apologist. But I'm also inclined to believe in observation. I was in the dissection room teaching anaesthetists a couple of weeks ago, when one of them complained that the cadaver "erroneously" showed a nerve in the wrong layer. Well, this was a real body he was arguing with.
For me, Leonardo's notebooks represent a triumph and a tragedy. How wonderful that we can see the workings of this man's mind, 500 years on. But how tragic that his own generation did not benefit from his discoveries. His notebooks lay unpublished for centuries. A few pages were copied and published as etchings at the end of the 18th century but it took until 1916 for all of Leonardo's anatomical papers to be published. They remain, to a modern anatomist's eye, utterly extraordinary and breathtaking in their scope and accuracy.
In science perhaps more than any other discipline, we stand on the shoulders of giants. Knowledge accumulates: a ratchet effect is produced. Observer
Leonardo da Vinci: Anatomist; Queen's Gallery, Buckingham Palace, London, to October 7.By Alice Roberts