Santiago Ramón y Cajal
Santiago Ramón y Cajal is often called the founder of modern neuroscience
It was his work that established the ‘neuron doctrine’ as the accepted model for the structure and function of the nervous system, and our modern understanding of the nervous system is founded on this doctrine.
Cajal was born in the Spanish Pyrenees in 1852. He spent his early years in the small village of Petilla, where his father was the local doctor. Later, the family moved to the university town of Zaragoza. Cajal was headstrong and rebellious. His father sent him to school but Cajal was dismissed for bad behaviour. After two apprenticeships, at a barber’s and a cobbler’s in the town, Cajal eventually returned to school and completed his education.
From an early age, Cajal loved to sketch and was a talented artist. His father, however, disapproved of this and wanted his son to study medicine. Cajal duly enrolled at Zaragoza University. Although he did not have an artistic career, Cajal’s talent did enable him to produce delicate and beautifully detailed illustrations of his discoveries, and these illustrations are admired to this day.
On graduating, Cajal was enlisted for military service. He was sent to Cuba, where he contracted malaria and dysentery, and in 1875 he was invalided home. Back in Zaragoza, he studied for his doctorate in medicine. Doctorate examinations were held in Madrid, and it was there that Cajal saw tissue samples under the microscope for the first time. He was so impressed by what he saw that he invested in a microscope and began his own investigations. But it was not until 1887, on another visit to Madrid, that Cajal would learn of the technique that would illuminate his future research.
In Madrid, Cajal met with neurologist Luis Simarro, who showed him samples of tissue taken from the cerebral cortex. The samples had been stained using a technique called Golgi’s stain (read more on the person who discovered this technique), which stains a random selection of individual cells in a sample, revealing the whole of each cell as a dark silhouette against a yellow background.
Although the Golgi method had been pioneered in 1873, Cajal had not yet encountered this technique and he was astonished by what he saw. He described seeing the outline of the cells as “sharp as a sketch with Chinese ink on transparent Japan-paper... Dumbfounded, I could not take my eye from the microscope.”
With this new technique at his disposal, Cajal returned to his laboratory. He improved Golgi’s method by repeating the staining process so the cells could be seen more clearly and in greater detail than before. Using this method, he studied tissue from different regions of the brain and from the brains of various species of vertebrates. He discovered that, rather than being fused together in a continuous web (as had previously been thought), the cells that make up the nervous system are in fact discrete units, separate from one another.
In 1888 Cajal published his findings. In his paper he described how, when examining a section of chick cerebellum, he had been able to observe axons ending freely. They ended in close proximity to other cells but were not fused with them. This disproved the reticular theory of the structure of the nervous system. It also led Cajal to a new understanding of how information is transmitted around the nervous system.
Reticular theory had suggested that – because the nervous system was a continuous web – impulses could travel through the whole network in all directions. Cajal’s discovery that nerve cells were independent required a new model for how the nervous system functioned. He proposed that electrical impulses were conducted through chains of nerve cells and that the direction of conduction is fixed. This is the ‘Law of Dynamic Polarization’, which states that impulses are conducted in a fixed direction through the neuron from dendrites, through the cell body, to the axon.
These discoveries are the central tenets of the neuron doctrine. They were published in Cajal’s magnum opus, ‘Textura del sistema nervioso del hombre y de los vertebrados’ (1899–1904). Cajal continued to conduct research and to teach until the end of his life. Despite his fame, he lived simply with his wife, Doña Silvería Fañanás García, with whom he had seven children.
Cajal received many honours, including the Nobel Prize in Physiology or Medicine in 1906, and the Spanish government built the Cajal Institute, for neurobiological research, in his name. When he died in 1934, he left all scientific belongings – including his books, drawings and microscopes – to the Institute; the collection is known today as the ‘Cajal Legacy’.Lead image:
Ting Low/Wellcome Images
Questions for discussion
- Cajal won the Nobel Prize in Physiology or Medicine in 1906. Who was the other, joint recipient of the prize that year? How were the two scientists connected?
- What are the four key points of the neuron doctrine? Try using the ‘further reading’ links listed below to find out.