Drawing the Nervous System

By Sheeva Azma

Despite being rivals, Camillo Golgi and Santiago Ramón y Cajal jointly won the 1906 Nobel Prize for Physiology or Medicine for, as the #NobelPrize website says, “revealing the inner beauty of the nervous system.”

Today, we take for granted the insights we have into our nervous system that have helped us develop cures to neurological diseases, live better, and even pursue neurohacking. I previously blogged about my love of the brain’s natural rewiring capabilities that we use throughout our lives (also called neuroplasticity). I’ve also written about the many high-tech brain imaging tools scientists and doctors use to understand brain structure and function. These advances are relatively new, though: did you know that, before the late 19th century, we did not have a good idea of what our brain cells even looked like?

In 1906, two scientists, Italian Camillo Golgi and Spaniard Santiago Ramón y Cajal, won the Nobel Prize for Physiology or Medicine “for revealing the inner beauty of the nervous system,” as the Nobel Prize website states. Golgi and Cajal developed ways to stain the cells of the nervous system (nerve cells) in order to see them more clearly and in detail, and to make sense of the wispy tufts of connections between different nerve cells. With the techniques developed by these two scientists, nerve cells could finally be seen more precisely under the microscope.

In 1875, Golgi published the first ever drawing of a brain cell (also called a neuron). The image showed the olfactory bulb of a dog, to be exact. It was first published in the Rivista Sperimentale di Freniatria e Medicina Legale in 1875.

photo of a drawing of a golgi stain of a dog's olfactory bulb by camillo golgi
Golgi’s drawing of an olfactory bulb in a dog was first published in 1875. Source: Wikimedia

Golgi had developed a new way to stain cells in the nervous system to make them easier to see under the microscope. This technique dyed individual nerve cells black so they could be seen more clearly under the microscope. This technique became known as Golgi staining.

Golgi staining allowed scientists to, for the first time, see nerve cells in the brain and spinal cord, highlighting different parts of these cells, such as the cell body (soma), axons, and dendrites. The Golgi staining method doesn’t visualize all cells, only a certain subset, and the selection procedures remain unknown. Nevertheless, Golgi’s work advanced what was known about nerve cell structure at the time.

photo of a drawing of a golgi cell by camillo golgi
Golgi’s drawing of a cell found in the cerebellum now called a Golgi cell. Source: Glickstein, 2006

Golgi’s contributions started to change how people thought about the structure of brain cells. Despite this, Golgi’s new technique sparked little interest among his fellow scientists until it caught the attention of Cajal, a scientist who, as De Carlos and Pedraza write, “almost always worked alone, usually in the solitude of his private laboratory installed at his home.” Cajal was a professor at a university, and he had access to the lab there, where he could conduct microscopic studies of the nervous system’s tissues (what’s called “histology”). However, research labs in Spain were rare and poorly equipped at the time. So, he also taught histology out of his home to make extra money while serving as a professor.

Santiago Ramón y Cajal in his laboratory in Spain. Source: Wikimedia Commons

Cajal studied Golgi’s work carefully after learning about it in 1887 from a colleague, Professor Simarro. Cajal improved upon Golgi staining to create his own beautifully detailed images of nervous system cells. Rather than dousing the nerve tissue in one long soak of silver nitrate as Golgi did, Cajal broke up the staining process into two shorter soaks, which visualized cells better and in more detail. His first paper using this novel approach characterized the nerve cells of the cerebellum in 1888.

photo of cajal's drawing of a purkinje cell of the cerebellum
One of Cajal’s drawings of the Purkinje cells of the human cerebellum. Source: Wikimedia Commons
photo of cajal's drawing of cells in the hippocampus of a rabbit
Cajal’s drawing of cells in the hippocampus of a rabbit. Source: Archive.org
photo of cajal's drawing of a section of spinal cord
Cajal’s drawing of a transverse section of the spinal cord. Source: Archive.org
photo of cajal's drawing of the structure of the retina (part of the mammalian eye)
Cajal’s drawing of the structure of the mammalian retina. Source: Wikimedia Commons

You can see more of Cajal’s nerve drawings here, here, and here.

Cajal’s work added evidence to what was called the ‘neuron theory’ at the time. According to the neuron theory, the nervous system was made up of cells which had distinct structures and functions. The neuron theory was a new theory at the time; Golgi himself had believed in a ‘reticular theory’ in which the nervous system was one unified blob of nerve fibers which all functioned as one. The two scientists therefore were at odds with each other, and continued to disagree bitterly, even after they were jointly awarded the 1906 Nobel Prize.

To learn more about Golgi, Cajal, and their contributions to modern neuroscience, check out the video from Neuro Transmissions below.

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