The Science of Leonardo: Inside the Mind of the Great Genius of the Renaissance
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Toward the end of 1507, Leonardo’s beloved uncle Francesco died in Vinci and left his entire estate to his favorite nephew. But the family, led by Ser Piero’s youngest son, challenged the will, and Leonardo had to go to Florence to plead his case. He was obliged to stay there for several months, until judgment was finally reached in his favor.52 During these months, Leonardo was the guest of the wealthy Florentine patron Piero di Braccio Martelli, an accomplished mathematician, who was also extending his hospitality to the sculptor Giovan Francesco Rustici.
According to Vasari, Leonardo was very fond of Rustici, who had been his fellow apprentice in Verrocchio’s workshop. Rustici, Vasari tells us, was not only an excellent sculptor but also a delightful eccentric who loved to host fanciful feasts and play elaborate pranks. He kept a large menagerie in his studio that included an eagle, a raven, numerous snakes, and a porcupine trained like a dog, which would occasionally rub its pricks against people’s legs under the table. Leonardo, who loved animals and was himself used to playing practical jokes, felt very much at home in the relaxed and playful ambience of the Casa Martelli and gladly participated in Rustici’s spirited entertainments. According to Vasari, he also helped the sculptor model a group of bronze statues for the Baptistery of St. John in Florence during that time.53
Leonardo’s main activity in Martelli’s house, however, was of a far more serious nature. He used his ample free time to bring some order into his vast collection of notes, dating from the previous twenty years. He threw himself into this enormous task with great energy, systematically reviewing the contents of all his Notebooks. But he soon realized that rearranging the entire collection was too ambitious a job. He decided, therefore, to limit himself to a more manageable task, assembling a few selections on his favorite subjects—water, anatomy, painting, and botany—about which he would write comprehensive treatises. “Begun in Florence, in the house of Piero di Braccio Martelli, on the 22nd of March 1508,” he wrote on the opening page of a new codex, now known as Codex Arundel. “This will be a collection without any order, made up of numerous sheets that I have copied here in the hope of later putting them in order in their proper places, according to the subjects they treat.”54 Over the following years, Leonardo mapped out the structure of his treatises in some detail and began to compose them. He may have finished some, although no full treatises are extant among the existing Notebooks today.
While reviewing his notes in Martelli’s house in Florence, Leonardo decided that human anatomy was an area he needed to revisit thoroughly. During the next four years he performed more dissections than ever before, and his anatomical drawings reached their highest degree of accuracy. He planned to publish a formal treatise on anatomy, and outlined it in great detail. During his first phase of anatomical studies, twenty years earlier, he had been concerned with the physiology of vision, the pathways of the nerves, and the “seat of the soul.” Now he concentrated on the grand theme of the human body in motion.
In his outline, Leonardo described in meticulous detail how he would demonstrate “in 120 books” the combined actions of nerves, muscles, tendons, and bones. “My configuration of the human body will be demonstrated to you just as if you had the natural man before you,” he announced, and he explained why this would require numerous dissections.
You must understand that such knowledge will not leave you satisfied on account of the very great confusion that results from the mix-up of membranes with veins, arteries, nerves, tendons, muscles, bones, and blood….
Therefore it is necessary to perform more dissections, of which you need 3 to have full knowledge of the veins and arteries, destroying with the utmost diligence all the rest; and another 3 to have knowledge of the membranes; and 3 for the tendons, muscles, and ligaments; 3 for the bones and cartilages; and 3 for the anatomy of the bones which have to be sawn through to demonstrate which is hollow and which is not….
Through my plan…there will be placed before you 3 or 4 demonstrations of each part from different aspects in such a way that you will retain a true and full knowledge of what you want to know about the human body.55
We do not know how many of the 120 chapters (or “books”) of his treatise Leonardo composed. However, the superb drawings that survived, which are now in the Windsor Collection, make it evident that his promises were not exaggerated.
In his Anatomical Studies, Leonardo gives a vivid description of the dreadful conditions under which he had to work. As there were no chemicals to preserve the cadavers, they would begin to decompose before he had time to examine and draw them properly. To avoid accusations of heresy, he worked at night, lighting his dissection room by candles, which must have made the experience even more macabre. “You will perhaps be impeded by your stomach,” he writes, addressing an imaginary apprentice, “and if this does not impede you, you will perhaps be impeded by the fear of living through the night hours in the company of these corpses, quartered and flayed and frightening to behold.”
It is evident that Leonardo needed a steely will to overcome his own aversion, but he persevered and carried out his dissections with the most delicate care and attention to detail, “taking away in its minutest particles all the flesh” to expose blood vessels, muscles, or bones until the corpse’s state of decay was too advanced to continue. “One single body was not sufficient for enough time,” he explains, “so it was necessary to proceed little by little with as many bodies as would render the complete knowledge. This I repeated twice in order to observe the differences.”56
While he was still in Florence going through his notes and planning his treatises, Leonardo was able to perform a postmortem on an old man he met by chance at the hospital of Santa Maria Nuova, where he had done his earlier anatomical studies, and who died in his presence. This dissection became a milestone in his anatomical work and led him to some of his most important medical discoveries. The story itself is highly significant and very moving. It shows how Leonardo was capable of performing his most precise dissections and scientific analyses without losing sight of human dignity:
And this old man, a few hours before his death, told me that he was over a hundred years old and that he felt nothing wrong with his body other than weakness. And thus, while sitting on a bed in the hospital of Santa Maria Nuova in Florence, without any movement or other sign of any mishap, he passed out of this life.—And I made an anatomy of him in order to see the cause of so sweet a death.57
Based on this anatomy, he brilliantly diagnosed that the old man had died from a thickening and narrowing of his blood vessels, the condition that became known as arteriosclerosis more than three hundred years after Leonardo discovered it.58
LAST YEARS IN MILAN
Upon his return to Milan, Leonardo continued his anatomical studies. He also began to assemble his numerous notes and instructions on painting into a sizable collection, known as Libro A (it has since been lost). From this collection, Francesco Melzi compiled the famous Trattato della pittura (Treatise on Painting) after Leonardo’s death.59 Among the many subjects in the Trattato are extensive observations on the forms and visual appearance of plants and trees. Most of these observations, which became known as Leonardo’s “botany for painters,” originated in Milan during the years 1508–12, when he devoted considerable time to botanical thought and drawings. Carlo Pedretti concluded that Melzi must have copied the botanical chapters of the Trattato from an entire lost manuscript on botany written by Leonardo.60
At the same time that he was working on his notes on anatomy, botany, and painting, and continuing work on the Leda and the Mona Lisa, Leonardo was asked by one of the king’s principal generals, Marshal Trivulzio, to design for him a tomb with a life-size equestrian statue.61 And so for the second time, almost fifteen years after abandoning the casting of il cavallo, Leonardo embarked on making extensive studies and designs for an equestrian statue in bronze. It was a project he would develop for three years, during which work on building the chapel for the Trivulzio monument had b
egun. But once again, external circumstances intervened. Political turmoil would soon engulf the city, and the bronze statue would never be cast.
In 1510, Leonardo had the good fortune to meet a brilliant young anatomist, Marcantonio della Torre, who had recently been appointed professor of medicine at the University of Pavia. Leonardo engaged Marcantonio in extensive discussions on anatomy, much as he had done with Luca Pacioli on geometry fifteen years earlier. Just as Pacioli had introduced him to the Latin editions of Euclid, the Greek authority on geometry, so della Torre likely introduced him to the Latin editions of Galen, the Greek authority on anatomy and medicine.62
Unfortunately, their discussions were short-lived. In the following year, della Torre died of the plague in Riva, where he had gone to treat victims of an epidemic. Nevertheless, this short association had a significant influence on Leonardo’s understanding of anatomy. His dissections took on a new level of sophistication, and he expanded his research far beyond the areas involved in the movement of the human body. He dissected various animals to compare their anatomies to human anatomy. And he began to delve further into the body to study the functions of the internal organs, respiration, and the flow of blood.
During this time the political landscape of Italy shifted again, and war broke out. In 1509, Louis XII, in alliance with the Vatican, had achieved a brilliant victory over the Venetians. But in 1510, Pope Julius II made peace with Venice and persuaded several European rulers to form a Holy League in order to drive the French “barbarians” from Italy. The French troops resisted for a while, but in December 1511 the League, using Swiss mercenaries to do the fighting, stormed Milan, expelled the French, and nominally installed Maximiliano Sforza, the young son of Ludovico, on the ducal throne his father had occupied.
Leonardo, finding himself once again unwelcome in the city that had treated him so well, retired to the Melzi estate in Vaprio on the river Adda, some twenty miles distant. Thanks to the generosity of the Melzi family, he and his entourage resided there comfortably for almost two years. While the political constellations in Italy continued to change, Leonardo calmly went about his research, dissecting animals, studying the turbulent waters of the Adda, and making a series of exquisite small-scale drawings of the surrounding regions. He also carried out extensive botanical studies in the spacious gardens of the estate and the surrounding areas. In exchange for the family’s hospitality, Leonardo produced splendid designs for the enlargement of the Villa Melzi, and for landscaping the gardens, some of which were realized in later years.63
FRUSTRATION IN ROME
Although Leonardo was comfortable in Vaprio, it was clear that he could not stay there indefinitely. Sooner or later he would have to find another patron who could provide him with the financial means to support himself, his household, and his continuing scientific research. Fortunately, such an opportunity soon presented itself. In February of 1513, Pope Julius II died in Rome, and Giovanni de’ Medici, the younger son of Lorenzo il Magnifico, was elected to the papacy under the name of Leo X. His brother Giuliano became commander in chief of the papal troops. With their support, the Medici, after an absence of almost twenty years, were able to reestablish themselves as the rulers of Florence.
Soon after his brother ascended to the papacy, Giuliano de’ Medici invited Leonardo to the papal court in Rome. The two had likely met at the court in Milan, and Giuliano was well aware of Leonardo’s reputation as a military engineer. Giuliano de’ Medici was also an eager student of natural philosophy. Leonardo could not have hoped for a more powerful and sympathetic patron, and when invited was only too glad to join the papal court.
In September 1513 he embarked on the journey to Rome with several of his pupils, including Francesco Melzi, and with numerous chests and trunks containing his personal belongings—his painting materials, probably some tools and scientific instruments, his voluminous Notebooks, and several paintings in various stages of completion, including the Leda, the Mona Lisa, and the Saint Anne. After traveling many weeks, the caravan reached Rome sometime in November or December.
Giuliano de’ Medici had prepared spacious quarters in the Belvedere, a luxurious villa near the papal palace inside the Vatican. Leonardo’s suite included several bedrooms, a kitchen, and a large studio and workshop where he could paint and conduct experiments. He was treated with deference and respect, and given everything he needed, including a regular allowance, without specific obligations. And yet, for Leonardo, this was not a happy time.
At sixty-one, he was now an old man. His long beard was white, his eyesight was failing. And though he was well respected—even venerated—as a great sage, he was no longer in fashion as an artist. His reputation as a painter had been eclipsed by younger rivals like Michelangelo and Raphael, who were both at the height of their fame. Both had painted magnificent frescoes in the Vatican—Michelangelo in the Sistine Chapel and Raphael in the so-called Stanze (Rooms), the private apartments of Pope Julius II. The new pope, Leo X, attracted scores of young artists to Rome and handed out lavish commissions, but none of them went to the old master from Florence. Although Leonardo once again was living in great comfort at court, he was no longer the center of the court’s attention. He felt lonely and depressed. It was during this time of uncertainty and discontent that he drew his celebrated self-portrait.64
Nonetheless, Leonardo continued his scientific studies with undiminished energy. Having been occupied with multiple projects for the past thirty years, working in this way had become second nature to him. His age may have slowed him down, but it certainly did not restrict or diminish his mental processes. After settling into his new home, he began extensive botanical studies in the sumptuous gardens of the Belvedere. He continued to explore the geometry of transformations, and designed a large parabolic mirror for capturing solar energy to boil water, which he thought could be useful to the dyers of textiles. And, he invented a machine for making rope, and a rolling mill for producing metal strips from which coins could be minted.65
He also continued his dissections, probably at the hospital of Santo Spirito, which was in the immediate vicinity of the Vatican. These dissections marked the last phase of his anatomical research, in which he concentrated on the processes of reproduction and the development of the embryo. Leonardo’s studies included highly original speculations about the origin of the embryo’s cognitive processes or, in his terminology, of the embryo’s soul.66 Unfortunately, these speculations contradicted the official Church doctrine about the divine nature of the human soul and were thus considered heretical by Pope Leo X. As a result, Leonardo was banned from conducting further autopsies or human dissections.67
Thus, in addition to being eclipsed as an artist, Leonardo now found himself prevented from continuing his research in embryology, his most advanced anatomical work. He may also have suffered from an illness in 1514.68 At any rate, he was given to morbid thoughts, filling his Notebooks with apocalyptic tales of floods and other terrifying catastrophes. However, simply writing about storms and floods was not enough for Leonardo. He also had to draw them and analyze them scientifically. The result was a series of a dozen extraordinary drawings in somber black chalk known as the “deluge drawings,” which are now a part of the Royal Collection at Windsor Castle and are accompanied by Leonardo’s powerful narrative of his apocalyptic visions. The narrative is strongly reminiscent of Leonardo’s description of how to paint a battle, composed twenty years earlier.69 Several pages long, it is full of horror, drama, and violence; there are highly emotional passages interspersed with detached, analytical ones, with precise descriptions of cascades and water and air currents, and detailed instructions on how to paint optical effects generated by storm clouds and falling rain. The overwhelming impression evoked by Leonardo’s narrative is that of despair, of the futility and frailty of human beings confronting the cataclysmic forces of the deluge. He writes in one passage:
One will see the dark gloomy air beaten by the rush of different and convoluting winds,
which are mingled with the weight of the continuous rain, and which are carrying helter-skelter an infinite number of branches torn from the trees, entangled with countless autumn leaves. The ancient trees will be seen uprooted and torn to pieces by the fury of the winds…. Oh how many will you see closing their ears with their hands to shut out the tremendous noises made in the darkened air by the raging of the winds…. Others, with gestures of hopelessness, took their own lives, despairing of being able to endure such suffering; and of these, some flung themselves from high rocks, others strangled themselves with their own hands…. 70
Figure 4-5: Deluge Study, c. 1515, Windsor Collection, Landscapes, Plants, and Water Studies, folio 59r
The drawings that illustrate his apocalyptic narrative are dark, violent, menacing, and disturbing. Nonetheless, they are astonishingly accurate in their renderings of water and air turbulence. Throughout his life, Leonardo had carefully studied the forms of waves, eddies, waterfalls, vortices, and air currents. Here, in old age, he summed up his knowledge of turbulence. Beyond their expressive emotional power, the deluge drawings can be seen as sophisticated mathematical diagrams, presenting a visual catalog of turbulent flows that would not look out of place in a modern textbook on fluid dynamics (see Fig. 4-5).