Leonardo da Vinci, Pathfinder of Science

by Henry S. Gillette

After having successfully diverted the Arno river, it was now necessary for Leonardo to return to the painting commissioned by the Signoria for its council chamber. But recently, Leonardo had suffered a rebuff in this work. Originally he had been given the whole room to do but now the opposite wall had been assigned to another man—Michelangelo Buonarroti. Leonardo had first met the young Michelangelo when he helped to judge the best location for Michelangelo’s monumental statue of David. The two men were opposites in every way. Leonardo, fifty-two years old, carefully dressed, cool and detached, was a man whose every action was the result of a thoughtful and analytical mind. Michelangelo, twenty-six years old, his clothes rumpled and covered with marble dust, was passionate and moody—an impulsive youth totally dedicated to art. They did not like each other, and now Leonardo was forced into a rivalry for which he had no heart.

The duel between these two giants of art aroused the whole of Florence and there was a constant stream of people watching them at work. Michelangelo was given a studio in the hospital of Sant’ Onofrio and Leonardo was working in the Papal Chamber in Santa Maria Novella. Among the many people who came to watch Leonardo was a young man of nineteen. He was already a pupil of Perugino and the experience of meeting and learning from Leonardo was to influence him the rest of his life. His name was Raffaello Sanzio—one of the great Renaissance painters of Italy and known to us by the name of Raphael.

While Leonardo worked at Santa Maria Novella he had the opportunity of continuing his studies in anatomy. Dissections at that time were novelties and when one was performed the doors were thrown open to the public. Leonardo must have attended the public dissections at the Church of Santa Croce. Now at Santa Maria Novella there was a hospital, and here Leonardo was able to continue his own dissections without interruption. In a cool room below the hospital where bodies were kept Leonardo worked late into the night. By the flickering lights of candles and in the silence of the world about him he studied, drew, and wrote in his notes of the wonders of the human body.

In a cool room below the hospital, Leonardo worked late into the night.

He performed autopsies on people who had died natural deaths—a special permission granted to him by the monks of the church, and among these autopsies are the first written reports of some of the diseases that are the causes of death. Arteriosclerosis, or stony growths in the blood vessels, and pulmonary tuberculosis, a nut-like growth in the lung, are among the discoveries Leonardo made in his lonely searches, although he did not use these medical names for them.

Above all Leonardo was attracted to the function of the muscles, especially those in the arms and legs. So faithfully, in fact, did he record the origin and insertion of all the various muscles that these drawings can be used as anatomical models today. Moreover, he believed that a good drawing was worth pages of words describing human anatomy. The muscles were rendered as cords so as to better understand their function. He described this function as one of pulling instead of pushing and he noted that for every muscle there is an opposing muscle. When one contracts the other expands. For example, when you tighten the biceps in your arm you can feel the looseness of the triceps, the muscle on the opposite side.

As the end of the summer of 1504 approached, Leonardo’s dream of the canal from Florence to the sea was destroyed. The summer had been hot and without rain. The water in the canal dried up and the Arno river returned to its original course. All the old arguments against the plan were revived. The Florentine army captains rebelled against the job of defending a useless project. Again Soderini and Machiavelli intervened. After heated debates in the Council of Eighty, which had been called into special session, Machiavelli himself was sent out to oversee the work. It was brought almost to completion when in late October disaster struck. The rains that had failed to come in summer fell from the heavens in great cloudbursts. Storm after storm swept the valleys. The workmen left and the soldiers were recalled. The Pisan army rushed in to fill up the diggings and one final storm washed away the dream to nothing but eroded mounds of dirt.

Leonardo buried his disappointment in other work. When the drawing for the Battle of Anghiari was ready for transfer to the wall of the council chamber, he had a special scaffolding made of his own invention which worked on the principle of a pair of scissors standing on end, with a long platform on top. As the legs were spread the scaffolding was lowered and when they were pinched together it was raised. The wall had been prepared with a special mixture which he hoped would bring out the brilliance of his tempera colors. With several assistants who had been assigned to him by the Signoria the violence of the Battle of Anghiari was transferred to the wall and the actual painting was begun.

During the winter months Leonardo would relax from his work on the huge painting and his dissections to roam the country around Florence. He visited the slaughterhouses where the animals were killed and prepared for market. Here he was able to examine the hearts of animals just slaughtered and to note that the heart retained its action until the body was almost cold. He made a glass model of the aorta (the main artery leading from the heart) of an ox with which he could experiment on the flow of the blood. He intended to add to it a glass tube for one of the semilunar valves of the heart. He also experimented with a frog, dissecting its brain, heart, and entrails and noted that it ceased to twitch only when the spinal cord was severed. In his notes, he wrote, “The frog instantly dies when the spinal cord is pierced; and previous to this it lived without head, without heart or any bowels or intestines or skin; and here therefore it would seem lies the foundation of movement and life.” He was of course searching for the reasons that muscles moved and from where the impulses originated.