Dissecting Leonardo's Anatomy
Water and Circulation
On the link between water and the heart:
"... he made a model of the aorta and aortic valve in glass ... with the the aid of such markers as grass seed to observe the pattern of eddies formed by the passage of blood through this valve orifice. This experiment was a direct extension of his observations on the flow of water in rivers and in experimental glass channels ..." (Keele xxix).
On the flow of blood to the fetus:
"First site a known comparison
with the water of river and then with the choler [yellow bile] which, when it
wishes to enter the stomach, goes to
the stomach against the course of the food which comes from the stomach. There
are two opposite motions which do not penetrate but give way to
one another as do rivers in their opposed currents" (qtd. in O'Malley 215).