The heart compared to a seed, c.1508 (pen & ink and chalk on paper) (recto...

In a famous note probably of 1508, Leonardo described witnessing, in the hospital of Santa Maria Nuova in Florence, the death of a man who claimed to be over a hundred years old, whereupon Leonardo conducted an autopsy ‘to see the cause of so sweet a death’. This double-sided sheet comes from the notebook compiled following that dissection, as an attempt to make sense of his findings; the actual dissection notes, which were presumably rapid, sketchy and stained with gore, do not survive. The largest study on the recto highlights the great vessels, the aorta at right (as we look at the sheet) and vena cava at left, with the azygos vein running vertically between them. Leonardo reveals both his tendency to stylisation and his partial reliance on animal as well as human subject matter: the form of the superior vena cava is too symmetrical, and the aortic arch with its single branch is configured as in ungulates such as the cow. But the more interesting study is the pair of sketches at upper left, in which Leonardo attempts to resolve the ancient debate about the centre of the venous system – whether the heart or the liver – by appeal to the analogy of a plant. The main block of text in the lower half of the sheet reads: All the veins and arteries arise from the heart. And the reason is that the largest veins and arteries are found at their conjunction with the heart, and the further they are removed from the heart, the finer they become, dividing into very small branches. And if you say that the veins have their origins in the liver because they have their ramifications there, just as the roots of plants have in the earth, the reply to this comparison is that plants do not have their origin in their roots, but the roots and other ramifications have their origin from that lower part of the plant which is situated between the air and the earth. And all the lower and upper parts of the plant are always less than this part which adjoins the earth ... and in consequence, the veins take their origin from the heart, where they are biggest. Accordingly at upper left Leonardo has drawn, on the left, the heart (labelled core) with the vena cava and the hepatic and renal veins, and on the right a peach stone (noccolo) with its branching stem and roots. The hepatic veins were thought to be analogous to the roots of the plant, as the liver was believed to be the source of 'nourishment', which was then carried by the venous system throughout the body The arterial system, by contrast, was thought to convey a life force known as 'vital spirit' from the heart throughout the body; an understanding of the circulation, and the connection of the arterial and venous systems, eluded Leonardo. But he did not accord the heart undue importance: while Aristotle may have believed that the heart was also the seat of intelligence and the emotions, Leonardo later stated that ‘the heart in itself is not the origin of life, but [simply] a vessel made of dense muscle vivified and nourished by an artery and a vein, as are other muscles.'