Why the old die: closing veins, and the veins of the earth
The notebook's dated opening, with an analogy between blood vessels, water channels and willow-lined banks
The leaf opens the notebook with a dated line, 'Begun in Milan on the 12th of September 1508,' then argues that death in the old comes about as the veins running from the spleen to the portal vein of the liver thicken until they close and cut off the nourishing blood. Leonardo generalises: the continual flow of blood makes veins callous and finally seals them, whereas the hollow 'veins of the earth' are instead widened by the long, continuous flow of water. He closes with a practical note that willow roots protect canal banks, and that willow branches set crosswise in the bank and cut low each year thicken into continuous shoots to make a living embankment all of one piece.
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Notebook begun in Milan, 12 September 1508
The leaf carries a dated incipit recording that the notebook was begun in Milan on the 12th of September 1508. It fixes the place and moment at which Leonardo started this book of notes.
Death in old age from thickening, closing veins
Death in the old without fever is caused, he writes, by the veins running from the spleen to the portal vein of the liver, whose coats thicken until they close and give no more passage to the nourishing blood. The blood's continual course makes such veins callous, so that in the end they seal themselves and forbid the blood its course.
The veins of the earth widened by water
Set against the animal's veins, which narrow and close, are the 'veins of the earth': their cavities, by the long and continuous course of the water, come instead to be widened. The passage draws an explicit parallel between the vessels of the body and the water channels of the earth.
Willows as a living reinforcement for canal banks
Willow roots, he notes, keep the banks of canals from being spoiled. Willow branches nourished crosswise in the thickness of the bank and cut low every year thicken into a mass of continuous shoots, giving a living bank all of one piece.