Leonardo da Vinci: Images of the Brain
Authors: Philo Ron , Petti Kevin 
Published: June 2021

Leonardo (1452–1519) produced hundreds of anatomical drawings from at least 30 dissections he conducted over a period of several decades. He began this endeavor to more accurately portray the human body; he continued the studies to create a treatise on human anatomy. In addition, numerous animal dissections and drawings were prepared by Leonardo. In 1490–1492 Leonardo drew an image (RL 12603r, K&P 32) in keeping with contemporary concepts that the cerebral ventricles and the psychic pneuma or animal spirits they contained were responsible for function of the brain. The ventricles are illustrated as three linear spaces with the optic nerves projecting to the ventricles. With this traditional view, Leonardo was perhaps the first to indicate the meningeal envelope of the optic nerves, and possibly the first to illustrate the frontal nasal sinus. Leonardo likened the coverings of the scalp and brain to layers of an onion, an analogy represented by the sectioned onion in the upper left image. Leonardo began to question connection of cranial nerves to the ventricles. This led him to prepare a wax cast of bovine cerebral ventricles to ascertain their true configuration. A hole was drilled through the underside of the skull, a syringe inserted into the 3rd ventricle and molten wax injected. For this first known example of casting of a body cavity, Leonardo applied the technique used in casting bronze statues. After the wax hardened, he removed the brain and dissected away the tissue. Leonardo then drew a series of studies on paper to illustrate the results (RL 19127r, K&P 104r). A drawing of the wax cast is at bottom right of this sheet. At top left, he has superimposed the cast onto the brain. At top right, Leonardo has drawn a brain with the ventricles in place, sectioned in the mid‐line from superior to inferior. In this image, the forebrain and midbrain are fully divided. Each half is retracted laterally. Below the level of the cerebral aqueduct, the hindbrain is only partially divided and the lower hindbrain remains intact. The central figure in the lower half of the sheet is an inferior view of the intact brain. The radiating feather‐like structure centered at the pituitary is a rete mirabile—present in cattle, not humans.

Even though Leonardo used a bovine specimen, the brain he has represented is human. There is a horizontal forebrain, a midbrain flexure and an inferiorly projecting hindbrain. This is indicative of an upright posture with a sub‐terminal foramen magnum as in man. A comparison of bovine and human brains in the accompanying figures indicates the proportions and configuration of brain components are human. It was not unusual at this period in anatomical history to transfer and transform structures from different species into the corresponding human structures. Human dissection was difficult to accomplish; animal dissection was not. In Rome, 1516, a disgruntled associate delivered a complaint against him to Pope Leo X and to hospital Santo Spirito, where he was performing his studies. Leonardo relocated to Amboise in the Loire valley under patronage of Francis I. He died 2 May 1519 at the chateau of Cloux. It would be several centuries before his studies were published.

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.