
Self portrait
By coincidence, I have read biographical works over the past several months about Isaac Newton, Albert Einstein, and Leonardo Da Vinci. In all three cases, the authors emphasized that these men were motivated by insatiable curiosities to question established “knowledge” and see beneath and beyond it.
The most recent of these books is “Leonardo’s Legacy” by European science writer Stefan Klein.
Although, Dan Brown aside, the mention of Leonardo may evoke in most people’s minds images of paintings and sculptures, Klein covers the broad range of Leonardo’s interests, from human anatomy to hydrodynamics.

Statue of Leonardo, Uffizi, Florence
Klein doesn’t neglect the arts. In fact, I found his discussion of the Mona Lisa enlightening. I am a duffer when it comes to art, and I have never thought seriously about that painting – which appears in so many contexts that it has become a cliche. But Klein’s explanation, for instance, of Leonardo’s use of chiaroscuro to create a lifelike image helped me to look at the portrait with a new perspective. The same is true of the author’s explanation of the painter’s use of light and of the landscape that appears in the background.
Klein also pointed out that Leonardo, who had made careful studies of the muscles and nerves that control facial expressions, created the woman in the “Mona Lisa” with an asymmetrical face in which the emotions expressed on each side are not identical. Here, Leonardo seemed to be anticipating what is now understood about the left and right hemispheres of the brain controlling the right and left sides of the body, respectively. It was one of many examples of how Leonardo applied what he learned in one field to his work in another.

Portrait by Swedish artist Evald Hansen
Leonardo associated with some interesting Renaissance characters, including the philosopher Nicolo Machiavelli and the warlord Cesare Borgia. Leonardo hired himself out to men like Borgia in order to make a living, and he earned his keep by providing entertainment and by designing practical devices, including weapons. Klein makes a point of the apparent contradiction between Leonardo’s abhorrence of war and avowed respect for life and his willingness to imagine and at least design on paper the most horrible mechanisms for maiming and killing human beings.
On the other hand, Leonardo’s employment by Borgia was the occasion for creating an astounding map of the Central Italian city of Imola. By Klein’s reckoning, Leonardo and an assistant paced off very street and building in the city, using instruments that Leonardo had invented for that purpose. Leonardo then prepared a realistic view of Imola that appeared as if it were viewed from overhead – an unheard-of concept at that time.

Flying machine design
Among Leonardo’s fixations was the behavior of water, and he spent incalculable hours pursuing it – simply by observing water in nature and also by sketching it alone and including it in his paintings. He studied surface tension and the manner in which water moved through wider and narrower channels. He put to use the knowledge he gained when he designed a lock for a canal in Milan and, in a more remote way, when he studied the manner in which blood flows through the vessels of the body. Klein suggests that Leonardo may have actually built a model of a heart to reach his conclusions about the movement of blood in the cardiac ventricles – something that wasn’t scientifically observed until hundreds of years later.

Anatomical drawings
Leonardo was also determined to provide man with the freedom of flight, but Klein explains that this enterprise was doomed to failure because of Leonardo’s incorrect assumption that birds could fly because they flapped their wings. Although Leonardo understood the concept of gliding, he did not deduce that birds kept themselves afloat because of the difference in the speed and pressure of air passing above and below their wings. Given the era in which he was working, however, Leonardo’s conceptual achievements in this area are still remarkable. In fact, Klein describes an experiment in which modern hobbyists built a machine based on one of Leonardo’s designs, but provided it with a rigid wing, and the device was able to fly.
A great deal of Leonardo’s insight – literally and figuratively – came from his work in dissecting cadavers, something that he found repugnant but pursued for the sake of knowledge. Study of anatomy was not unusual among artists at that time, but Leonardo’s desire to understand the component parts of any organism – natural or artificial – took his studies far beyond those of his contemporaries. His study of the body of a centenarian with whom he had been acquainted led him to the conclusion that the man had died because hardened and constricted vessels had retarded the flow of blood, a finding that foreshadowed diagnoses of arteriosclerosis. So thorough were Leonardo’s examinations of the human body that Klein says some of the artist’s anatomical drawings could have been made in the 21st century.
The author argues that Leonardo’s expansive work was possible because the manner in which he lived gave him a great deal of freedom to observe and ponder and sketch and tinker. Klein speculates that minds like Leonardo’s still exist but wonders if they can thrive under our highly structured educational systems.
In any event, this very readable book challenges us all by reminding us of the capacity of the human mind, even ours.

Leonardo's "overhead" map of Imola. The roof of each individual house was painted in water colors.