Drawing the Nervous System

Image: Cortical Pyramidal cells of the brain. The Cajal Institute

Santiago Ramón y Cajal, Spain 1852

Santiago Ramón y Cajal is known as the father of modern neuroscience and a Nobel prize-winning pathologist. His main accomplishment is the Neuron Doctrine which explains the appendage that enables neurons to make precise synaptic connections with other neurons (Figure 1). Cajal became “recognized because of his uncanny sense of the functional implications of his work.”10 A sense that as an artist let him propose theories and depict them based on what he saw through the microscope combining scientific knowledge and research of the brain’s microscopic structure. The precise representation pushed the study of neuroscience forward through detailing the seemingly endless interconnected brain cells.11

After graduating from the University of Zaragoza, he moved to Barcelona. This is where Cajal adopted the Golgi method of silver-staining in 1887 and when he developed all of his most important research of the brain. This method greatly enhanced the ability to study nerve cells, by modifying the Golgi method improving its capabilities. (Figure 2) To Cajal, the Golgi method was the most important invention in which he stated so poetically, ”Could the dream of such a technique truly become a reality, in which the microscope becomes a scalpel and histology a fine tool for anatomical dissection?... What an unexpected spectacle!”.12 Although, the method was not widely used within the scientific community at the time.

With the new Golgi method Cajal turned his attention to the central nervous system, brain, and spinal Cord (Figure 3), making detailed drawings of neural material covering tissue samples from different parts of the brain. At the time, microphotography was not available, which meant that scientists would have to illustrate their findings as accurately as they perceived it, highlighting areas that they deemed “most important”. Decades can pass by with scientists seeing the same set of images, but if none of them accurately depict it, the discoveries go unnoticed. Cajal’s observations using the Golgi method were, in this case, the most accurate of the scientific community. He concluded that the brain was made up of individual cellular elements called neurons, unlike the previous belief that the nervous system was a continuous network or web of elements.13 Instead, he proposed that the nerve cells receive information from the dendrites carrying information into other nerve cells. With this he created the basis of how neural connections work, winning the Nobel prize in 1906, in which the electron microscope proved his findings and assumptions to be correct decades later.

When Cajal drew accurate depictions of the nerve cells, he inferred connections not clearly seen in the microscope at the time, which helped propose his neural doctrine. His drawings were thoughtful depictions not of what is but of what matters and of his hypothesis. He first drew in pencil depicting everything he could see under the microscope in detail. Later; later, he fixed errors and meticulously inked the drawing. These were not merely sketches, but some of the most accurate depictions of the specimen and the brain still in use today. After drawing the hundreds of samples taken from the brain, he inferred the circuitry that makes up the neural network by putting moments of his illustrations together to conclude the more extensive connectivity at work.

At first, the illustrations look closer to a diagram used in architectural representation to describe global physiological functions. Cajal sliced sectional parts of the brain to see the neurons’ interconnectivity in the nervous system, much like a section in an architectural drawing that produces connections between programmatic elements. To Cajal, the most critical areas to illustrate were “the general form, the common properties and the essence of the specimen’s overall architecture”14. Furthermore, he embedded functional qualities into his drawings, like technical drawings illustrate electrical and plumbing connections through central points in the building’s systems. A technical drawing, in this case, is akin to the neuron with their dendrites reaching out to the next one relaying information to each other by creating the brain’s neural forest, which is the work he is most known for.

Cajal’s illustrations are now in the Cajal Institute in Madrid, Spain, the most extensive collection of his work, with over 3,000 drawings cataloged after the second world war.15 These illustrations are still in use today at universities and institutions. Cajal’s scientific and illustrative practice questioned the problem of visualization, interpretation, and representation in scientific research16. However, it opened up a path towards a larger understanding of the world around us using science and the art of representation.

Suggested readings:

Santiago Ramón y Cajal: The Nobel Prize in Physiology or Medicine 1906”. NobelPrize.org. Retrieved 2020-06-25.

Santiago Ramón y Cajal, Recuerdos de mi Vida. Volume I, Madrid Imprenta y Librería de N. Moya, Madrid 1917, online at Instituto Cervantes

Finger, Stanley (2000). “Chapter 13: Santiago Ramón y Cajal. From nerve nets to neuron doctrine”. Minds behind the brain: A history of the pioneers and their discoveries. New York: Oxford University Press. pp. 197–216. ISBN 0-19-508571-X.

Newman, Eric A., Araque, Alfonso, Dubinsky, Janet M., Swanson, Larry W., King, Lyndel Saunders, Himmel, Eric. The beautiful brain: the drawings of Santiago Ramón y Cajal. New York. 17 January 2017. ISBN 978-14197-2227-1. OCLC 9389913

Llinás, R. The contribution of Santiago Ramon y Cajal to functional neuroscience. Nat Rev Neurosci 4, 77–80 (2003).

Fields, R. Douglas. Why the First Drawings of Neurons Were Defaced. September 2017.

DeFelipe J. The dendritic spine story: an intriguing process of discovery. Front Neuroanat. 2015 Mar 5;9:14.

Noë, Alva. The Art Of The Brain, On Exhibit. January, 2017.

Schoonover, Carl. Portraits of The Mind: Visualizing the Brain from Antiquity to the 21st Century. Harry N. Abrams, 2010, ISBN 0810990334, 9780810990333 Figure 7 (top): Photomicrographs of Cajal’s original histological preparations housed at the Cajal Institute

Figure 1 (top): Neuroscience sketch, The Cajal Institute Figure 2 (bottom): Neurologic Sketch, The Cajal Institute

Figure 3 (top): Neurology diagram, The Cajal Institute Figure 4 (bottom): Neurology diagram, The Cajal Institute

Figure 5 (top): Cortical Pyramidal cells of the brain. The Cajal Institute Figure 6 (bottom): Spinal cord and brain. The Cajal Institute