Santiago Ramón y Cajal

Chapter 1 · The Cannon and the Cobbler

A boy his father could do nothing with

1852 – 1873 · Petilla de Aragón · Ayerbe · Zaragoza

Santiago Ramón y Cajal was born in May 1852 at Petilla de Aragón, a mountain village, the son of Justo Ramón, a village surgeon who had raised himself from real poverty by sheer effort and expected the same of his son.

He got, instead, a child who was expelled from school repeatedly, ran away, and was — by his own account in his autobiography — imprisoned at eleven for building a cannon out of a piece of pipe and firing it at a neighbour's new wooden gate, which it destroyed.

He wanted to be a painter. He drew constantly and was good at it. His father regarded art as a route to starvation and refused absolutely, and apprenticed him instead to a barber and then to a cobbler, to teach him what a life without education looked like.

Then the father tried something else. He took the boy to a graveyard at night to collect and draw human bones for anatomical study. It worked. Cajal discovered that anatomy would let him draw, seriously, all day, and that the drawing was the work rather than a distraction from it.

He qualified in medicine at Zaragoza in 1873 and was conscripted as an army doctor, serving in Cuba during the Ten Years' War. He caught malaria and tuberculosis, came home seriously ill, and spent a long convalescence.

He bought a microscope with his back pay.

“Every man can, if he so desires, become the sculptor of his own brain.”

— Santiago Ramón y Cajal, Advice for a Young Investigator (1897)

Why this matters

Cajal's frustrated ambition to be a painter is not a colourful detail: his anatomy is a drawing practice, and the drawings are the evidence.

You have the cannon, the cobbler's bench and the graveyard. What would you ask?

Ask Cajal

• “Did you really fire a cannon at a neighbour's gate?”
• “Why would your father not let you be a painter?”
• “What did drawing bones in a graveyard change?”
• “What was Cuba like for an army doctor?”
• “Why buy a microscope with your army pay?”

Chapter 2 · A Stain That Blackens Only a Few

Madrid, 1887

1887 · Madrid · Valencia · Barcelona

In 1887 Cajal travelled to Madrid and saw, in the laboratory of the psychiatrist Luis Simarro, preparations made with Camillo Golgi's *reazione nera* — the black reaction, published in 1873 and largely ignored for fourteen years.

The stain does something strange and extremely useful. Treat nervous tissue with potassium dichromate and then silver nitrate, and a small, apparently random fraction of the nerve cells — perhaps one in a hundred — is impregnated with silver and turns completely black, in every branch and twig, right to the finest ending. The other ninety-nine remain invisible.

Why this matters is a problem of *density*. Nervous tissue is packed so tightly with interwoven fibres that a stain colouring everything produces an impenetrable black felt in which nothing can be traced. Golgi's stain gives you one cell at a time, complete, against an empty background.

Cajal understood at once what it was for, and made two changes that transformed it. He repeated the impregnation, doubling the process to get more consistent results. And — the crucial move — he applied it to *embryonic and very young* nervous tissue rather than adult.

The reasoning is simple and it is the whole trick. In a young animal the nerve cells are smaller, far less branched, and not yet wrapped in myelin. The forest has fewer branches and no fog. You can follow a fibre from one end to the other.

Nobody else had thought to look at the immature brain.

Why this matters

Cajal's decisive innovation was choosing young tissue, where nerve cells are simple enough to follow — a change of specimen, not of instrument.

You have the stain that blackens one cell in a hundred. What is your question?

Ask Cajal

• “Why is it useful that the stain misses most of the cells?”
• “Why look at young brains rather than adult ones?”
• “Why had Golgi's stain been ignored for fourteen years?”
• “How do you improve a method somebody else invented?”
• “What does nervous tissue look like when everything is stained?”

Chapter 3 · Separate Cells, Not a Net

The neuron doctrine, and the direction of the impulse

1888 – 1891 · Barcelona · Madrid

The accepted view — the *reticular theory*, held by Golgi and by most of Europe — was that the nervous system is a continuous network. Nerve fibres fuse into one another, forming a single uninterrupted web through which excitation spreads. On that account the brain is not made of units at all.

Cajal, following individual cells through young tissue, saw something different everywhere he looked. A cell's branches ended. They came very close to the next cell — sometimes wrapping around it, sometimes forming dense baskets — but they did not join. Each cell was a separate individual, contiguous but not continuous.

He called 1888 his greatest year. He founded and paid for his own journal to publish it, because no Spanish outlet was suitable and nobody abroad was reading Spanish anatomy.

He also worked out the *direction*. From the structure of cells in the retina and the cerebellum, where the input and output are geometrically obvious, he argued that signals pass into a cell through its branching dendrites, through the body, and out along the single long axon — the law of dynamic polarisation. Nerve cells are not passive conduits; they have a direction built into their shape.

In 1889 he took his preparations to the German Anatomical Society meeting at Berlin and simply set up his microscopes and made people look. Albert von Kölliker, the leading anatomist in Europe, looked, was convinced, learned Spanish, and became his advocate.

Why this matters

The neuron doctrine — that the brain is built of separate cells rather than a continuous net — is the foundation on which all of neuroscience rests.

You have the branches that come close and do not join. What would you ask?

Ask Cajal

• “How can you tell two cells touch without joining?”
• “What made you sure the impulse travels one way?”
• “Why found your own journal?”
• “What happened when you made Kölliker look down your microscope?”
• “What does the reticular theory get right?”

Chapter 4 · Drawing as Evidence

Thousands of figures, still reproduced

1888 – 1934 · Madrid

Cajal produced somewhere near three thousand drawings, and they are still printed in neuroscience textbooks — not as historical illustrations but as teaching figures, because they are clearer than photographs.

That needs explaining, because it sounds like sentiment. It is not. A photomicrograph records one focal plane. A neuron is a three-dimensional object whose branches wander through the depth of a thick section, so no single photograph can show it whole; parts are always blurred. Cajal focused up and down through the specimen, holding the whole structure in his head, and drew the cell as it actually is — a synthesis of many planes into one image.

He drew from memory, after the observation, rather than tracing. He described the process: look until you understand what you are looking at, then draw what you understand.

That carries an obvious risk. A drawing made from understanding rather than from tracing can encode an interpretation as though it were an observation, and Cajal knew it. His defence was that the drawings must be checkable — anybody with the stain and the tissue could go and look — and they were checked, repeatedly, and they hold up.

He also worked on the *growth cone*, the swollen exploring tip of a developing nerve fibre, which he described as a kind of battering ram feeling its way through tissue. That is now the basis of the whole study of how a nervous system wires itself.

He was also a serious photographer, wrote on colour photography, and published a collection of short stories.

Why this matters

A drawing can show a three-dimensional neuron whole in a way no single photograph can, which is why Cajal's figures are still the clearest teaching images available.

You have three thousand drawings made from memory. What is your question?

Ask Cajal

• “Why is a drawing better evidence than a photograph here?”
• “How do you stop a drawing from encoding what you expect?”
• “What is the growth cone doing?”
• “Did the painter you wanted to be ever go away?”
• “Which of your drawings took the longest to get right?”

Chapter 5 · Sitting Beside the Man Who Would Not Concede

Stockholm, 1906, and a wrong belief that cost decades

1906 – 1934 · Stockholm · Madrid

In 1906 the Nobel Prize in Physiology or Medicine was awarded jointly to Camillo Golgi and Santiago Ramón y Cajal, for their work on the structure of the nervous system.

Golgi lectured first. He used the occasion to attack the neuron doctrine and to restate the reticular theory, arguing that the nervous system is a continuous net, while Cajal sat in the hall waiting to speak. Cajal, in his own account, found it painful and improper, and gave his own lecture setting out the evidence.

Both men had genuinely earned the prize — Cajal depended entirely on Golgi's stain and always said so — and they never reconciled.

Cajal was, on one important point, wrong, and it cost the field decades. He held that the adult nervous system is fixed: that nerve pathways are, in his phrase, something fixed, ended and immutable, and that once development is over nothing can regenerate. He had good evidence for it in the central nervous system. But the conclusion, stated with his authority, discouraged serious research into regeneration and plasticity for most of the twentieth century, and both turn out to be real.

He also could not settle the crucial point of his own doctrine. His microscopes could not resolve the gap between two nerve cells. Charles Sherrington named that junction the *synapse* in 1897 on functional grounds, and it was only seen directly with the electron microscope in the 1950s, twenty years after Cajal's death.

His son Santiago died young, and he never recovered from it. He died in Madrid in October 1934, aged eighty-two.

Why this matters

Cajal's authoritative belief that the adult nervous system cannot change discouraged research into regeneration and plasticity for most of a century.

You have Stockholm, the unresolved gap and the belief that held the field back. What would you ask?

Ask Cajal

• “What was it like hearing Golgi attack your work at the ceremony?”
• “Did Golgi deserve to share the prize with you?”
• “Why were you so sure the adult brain cannot change?”
• “You never saw the gap between two cells — did that worry you?”
• “What would you tell a young investigator starting now?”

What Cajal changed

The neuron doctrine — that the nervous system is built of separate cells that touch without joining — is the foundation of neuroscience, and Cajal's hand-drawn figures are still used to teach it because they show a three-dimensional cell whole in a way no photograph can. He also established that the impulse travels through a nerve cell in one direction, and described the growth cone that guides a developing fibre.

A debate that continues

Cajal's insistence that the adult nervous system is fixed and cannot regenerate was stated with great authority and turned out to be wrong, discouraging research into plasticity for decades; and the synapse he inferred was not directly observed until the 1950s.

Keep exploring — ask Cajal

• “Which drawing would you redo with what is known now?”
• “How should a scientist behave when they are proved wrong?”
• “Was your father right to stop you painting?”

Related lives

• Theodor Schwann — Who Said Animals Are Built Like Plants
• Claude Bernard — Father of Experimental Medicine
• Hans Spemann — Who Imagined the Experiment First
• Ernest Starling — The Man Who Named the Hormone

Related themes

The nervous system · Neurones and synapses · Microscopy and evidence