Neurons in the spinal cord of a snake embryo; drawing by Santiago Ramón y Cajal

Cajal Institute/Cajal Legacy/Spanish National Research Council (CSIC)

Neurons in the spinal cord of a snake embryo; drawing by Santiago Ramón y Cajal, 1899

In 1918 the Spanish neuroanatomist Santiago Ramón y Cajal began writing down his dreams. Some were brief—“I attend a diplomatic soiree and as I am leaving my pants fall down”; “Thieves break in. And I said to them: do not kill me, and they took out a revolver but later it turns out it was only a toy just to frighten me”—and some were a little longer. He is invited to an engineer’s house and is served a meal, which he eats while the engineer’s wife watches him; she is pleased at his good appetite, having heard that he was ill and on a diet. When the subject of her husband arises, Cajal says, “Excuse me, I hardly know the professors from the school of civil engineering.” As if to refute the possibility that the dream had any importance, he adds, “Inconsistencies: for many years I have not eaten outside the house. I do not know the wife of any engineer intimately enough that they would invite me to eat.”

Cajal believed that dreams were produced in “the fallow lands of the brain,” from “scraps of ideas, unconnected or weirdly assembled,” and that they had no “harmony or reason.” In 1908, two years after he won the Nobel Prize in Physiology for “work on the structure of the nervous system,” he wrote a paper about a man who had gone blind as an adult but could still see in his dreams. He concluded that the brain could conjure images without using the eyes. The paper ended, “To be continued…” Cajal began writing down his dreams because he believed it might help him discover how they were invoked.

Benjamin Ehrlich, in The Brain in Search of Itself, a new biography of Cajal, says that Cajal’s interest in dreams was motivated in part by “his hatred of Sigmund Freud.”* Around 1911 Ortega y Gasset wrote that Freud was “trying to make psychophysiology lead into biology.” Ehrlich says that Cajal “was trying to do the exact opposite.” In Madrid, where Cajal was living, the intellectual class “treated Freud’s theories as though they were biological realities, while Cajal considered them ‘collective lies.’” Cajal thought that Freud’s propositions were “pseudoscientific” and “impregnated with mysticism.” In a letter, he wrote:

Except in extremely rare cases it is impossible to verify the doctrine of the surly and somewhat egotistical Viennese author, who has always seemed more preoccupied with founding a sensational theory than with the desire to austerely serve the cause of scientific theory.

Cajal’s stance has about it, too, the antipathy of a rival. According to Ehrlich, Cajal was worried that Freud “was eclipsing his fame.”

Whereas Freud saw consciousness as layered and broadly situated in the brain, Cajal saw it as local and mechanical. He believed that it resided somehow within cells, as if a cell were a kind of chamber containing impressions that produce the self and one’s sense of being alive. By mapping the pathways of thinking, Cajal hoped to cast light on “the utter darkness of the inner mechanism of psychic acts.”

In 1892 Cajal announced that he had discovered a nerve cell that had a triangular shape. He called it the “pyramidal cell” and said that it was common to all vertebrates. The more highly evolved the animal, he claimed, the larger and more complex the cell was. “He suggested—albeit ‘with some reservations’—that mental function must be related to pyramidal cells, which he took to calling ‘psychic cells,’” Ehrlich writes. A journalist described Cajal’s research as “the sketch of an anatomical doctrine of intelligence.” A German researcher wrote that his work on the elemental structures of the brain had created the basis for “a Psycho-Physiology that is not subject to the mystical element.”

Cajal shared his Nobel with the Italian scientist Camillo Golgi, who had invented a technique for staining nerve cells so that they could be seen clearly under a microscope; he called this the black reaction. Each man is described by supporters as “the founder of modern neuroscience,” but Cajal’s claim is stronger. Golgi invented the method with which Cajal discovered that nerve cells are not linked to one another but are individual and have spaces between them—what is now called the neuron doctrine. Ehrlich writes of Cajal that “historians have ranked him alongside Darwin and Pasteur as one of the great biologists of the nineteenth century and among Copernicus, Galileo, and Newton as one of the greatest scientists of all time,” but he doesn’t supply sources for these assertions. Like those others, though, Cajal discovered an order in nature that hadn’t been apparent.


Cajal was also an exceptional draftsman, and his highly specific drawings of nerve cells are what he is more widely remembered for. They are beautiful and strangely dreamlike, as if excavated intact from the unconscious. Despite being realistic, they seem cousin to some of Paul Klee’s symbolic arrangements of obscurely suggestive forms. Cajal’s drawings, which are still reproduced in textbooks and appear in galleries and museums, are composite. He would stain a slice of brain tissue using the black reaction, study it through a microscope, go out to a café, then come back and draw the image from memory. A literal version, he believed, would have been so detailed as to be incomprehensible.

Cajal was born in 1852 in a remote village in the mountains of northeast Spain. His father, Justo, was from a line of impoverished farmers. At sixteen or seventeen Justo left the farm and became an apprentice to a barber-surgeon, which was the lowest member of the medical class, beneath doctors and surgeons. Like many country people in Spain at the time, Justo was illiterate. He taught himself to read—probably by matching the procedures in the barber-surgeon manuals with those he was learning—and discovered that he was able to memorize entire texts. This led him to go to school and become a surgeon.

Cajal described himself as a child as a “wayward, unlikeable creature.” Having been tutored by his father, he was ahead of other boys when he started school, but eventually he was required to memorize texts, which he couldn’t do. Worried about disappointing his father and perhaps trying to deflect attention from his difficulties, he began skipping classes and cutting up when he attended them, to which Justo responded by whipping him until he bled and beating him with a club. Cajal withdrew into his imagination. Around the age of ten he developed an “irresistible mania” for drawing. He told his father that he wanted to be an artist, but Justo “considered artistic expression a developmental defect, an illness of the will,” Ehrlich writes. He confiscated Cajal’s paper and pencils and burned his drawings, so Cajal drew secretly and hid his drawings in the fields.

In 1869, when Cajal was seventeen, he enrolled in the medical school in Zaragoza, where his father had been trained. He finished in 1873, with a license in surgery, and was drafted; the following year he was sent to Cuba, where there was a revolt against the Spanish colonists. After a few months he got malaria, and after about a year he was forced to apply for a medical discharge. “He had left Spain at the peak of his physical powers, and he had returned sick and enfeebled,” Ehrlich writes. Cajal was briefly a surgeon in a village about thirty miles from Zaragoza, a position Justo had arranged without consulting him. He stayed only long enough for Justo not to be publicly embarrassed by his leaving, then he set up a lab in his parents’ attic, where he read textbooks and reproduced the writers’ experiments, a method his father had taught him to reinforce his learning.

When Cajal was a student most Spanish doctors believed in vitalism, an antique notion that life is sustained by an obscure and immaterial force, something like a soul. According to vitalism, when a body was sick, the vital force effected a cure. Cajal believed instead in cell theory, the idea proposed in 1839 that cells are the basic elements of life. The body’s response to disease took place at the cellular level, the cell being, Cajal wrote, “the exclusive actor in pathological events.” Cajal had read about cells, but he hadn’t seen any, since there were very few microscopes in Spain. The only one in Zaragoza was in the medical school’s physiology department, and one day an assistant in the department invited Cajal to look at some slides. He saw blood cells circulating in the body of an anesthetized frog and “felt as though I were witnessing a revelation,” he said.

The first person to publish a report of what he saw through a microscope was the British scientist and architect Robert Hooke. Looking at a slide of cork in 1665, Hooke saw a succession “of empty boxes, which reminded him of the living quarters of monks,” Ehrlich writes, and he called them cells. Nerve cells have a body, or a room, and long, thin filaments—axons and dendrites. Axons carry information away from the cell and dendrites receive it. These structures can be seen clearly after a cell has been stained. In Cajal’s time the accepted methods revealed cell bodies, but the axons and dendrites looked like bundles of fibers—Cajal said he could see only “a tangled thicket.”

Cajal’s other doctrinal conflict was with reticular theory, the period’s explanation for the design of the nervous system. Rather than a system where the cells were independent of one another, reticular theory said that the nervous system was a single structure, with the axons and dendrites connected. Something felt by part of the net was felt by the whole. Cajal thought this unworkable, since a single, continuous system would mean that the brain received stimuli at the same time as it was responding, which would be too chaotic to manage. Furthermore, Cajal wrote:


A continuous pre-established net—like the lattice of telegraphic wires in which no new stations or new lines can be created—somehow rigid, immutable, incapable of being modified, goes against the concept that we all hold of the organ of thought, that within certain limits, it is malleable and capable of being perfected by means of well-directed mental gymnastics.

According to Ehrlich, Cajal aspired to “answer the most important question facing anatomists of his generation: How are the elements of the nervous system related?” Proving that the cells did not connect to one another in a latticelike structure but were discrete, and that axons and dendrites were more like roots or branches with spaces between them—synapses across which thoughts and impressions and impulses pass—would mean that the “nervous system would be the final territory conquered by cell theory.”

Reticular theory was widely embraced, however. In 1877 a researcher in England named Edward Sharpey-Schafer had found that nerve fibers in jellyfish, even though they are entangled, do not connect to one another. Sharpey-Schafer regarded the discovery as astounding and almost difficult to believe. He sent his report to the Royal Society and wrote on the envelope, “So far as I know, this paper contains the first account of a nervous system being formed of separate nerve units without anatomical continuity.” The society doubted his research and asked him to withdraw it.

A psychiatrist Cajal met showed him the black reaction, which Golgi said could make plain the nervous structure “even to the blind.” Golgi’s method, however, sometimes produced accidental results, which are called artifacts. One researcher said that it “suggests rather than demonstrates.” By the time Cajal began using the black reaction, in 1886, it had mostly been given up. Cajal assured himself that he wasn’t seeing artifacts by reproducing his results with other methods.

When, by means of the black reaction, Cajal saw that nerve fibers are independent of one another, he published the result himself in 1888. He could afford to print only sixty copies, which he sent to researchers around the world. By many in Europe, Spain was thought to be backward and incapable of serious science. In addition, Cajal had published his results in Spanish, which not many scientists read. When no one responded, Cajal wrote that he was “a little alarmed by the silence.”

In October of 1889 Cajal went to a conference in Berlin with his microscope and slides and set them up on a table in a corner, where for the most part he was overlooked. At the conference was a Swiss researcher, Albert von Kölliker, whom every scientist at the conference was hoping to impress. “Cajal practically dragged Kölliker to his corner of the demonstration room,” Ehrlich writes. Kölliker did not believe in reticular theory, but he didn’t feel he had seen anything to prove that nerve fibers were not connected, either. He looked through Cajal’s microscope, saw that the nerve fibers were independent of one another, and said that he was “enchanted.” Hearing of Kölliker’s endorsement, other scientists lined up to look through the microscope. “The obscure Spaniard had finally made his name,” Ehrlich writes.

Early on October 26, 1906, a messenger knocked on Cajal’s door with a telegram informing him that he had won the Nobel Prize. He thought that his students were playing a joke on him and ignored it, but the next day he saw his photograph in the newspaper. After the prize, it was said that a letter could be sent to Cajal with his name and “Madrid” on the envelope. His brother, Pedro, visited Portugal while on vacation; he was greeted by a local band, fireworks were lit, he was given flowers, and a crowd chanted his name. When Pedro said he was not who they thought he was, but only his brother, someone shouted, “Long live the brother of the genius Spaniard Santiago Ramón y Cajal!”

During World War I Cajal was asked by a weekly newspaper to respond to a question about what “political, emotional, and ideological trends will dominate Europe in the future.” He wrote that he had “a very low opinion of human beings,” who, as a race, display the “foul instincts” of beasts. “Our nerve cells continue to react in the same way as in the Neolithic Age,” he said. Neurons are adaptable, but their adaptability is restricted by an “evolutionary resistance,” which made him feel that war was a permanent feature of human life. Civilization could only hope to prolong episodes of peace. The “destructive phase” always reappears, and each iteration of war is more horrible than the last.

Toward the end of the war, Cajal began to have migraines. The first made him feel as though his head were on fire. When a doctor told him that his arteries were hardening and interfering with the flow of blood to his brain, he wondered if having worked so hard had led to “permanent brain congestion.” Meanwhile he worried that his work might be forgotten. In his sixties, Cajal began to lose his hearing. His friends and family had to shout when they spoke to him, which made them hoarse, so they began to whisper, leading him to think that they had lowered their voices in order to talk about him. “After all those years,” Ehrlich writes, “he concluded, people had finally realized the truth about him, which he had feared since he was a child: that he was unlikable.”

Even after Cajal won the Nobel Prize, he answered all his mail. A man wrote from Germany to say he had invented a hat that ventilated the brain. A schoolteacher sent him a butterfly, and he sent her a “scientific summary of the creature.” In 1929 a man he had known in Cuba wrote that his cousin had appeared in a dream and asked him to congratulate Cajal, saying that he would then make a new discovery. Cajal wrote back, “I am very old and sick and I do not expect to make any discoveries anymore.”

A few hours before he died, on October 17, 1934, he wrote:

I leave you something greater than any wonder of the senses: a privileged brain, sovereign organ of behavior and action, which used wisely will immeasurably improve the analytical power of your senses. Thanks to it you can dive into the unknown and operate on the invisible, elucidating, as much as possible, the obscure questions of matter and energy (hidden from the common man); your inquisitive power shall be far from exhausted; in fact, it shall expand interminably so far that each evolutionary phase of Homo sapiens will don the characteristics of a new humanity.

Sometimes the detail that Ehrlich goes into is fatiguing, but biography, like reporting, rewards comprehensiveness. Ehrlich is truly fascinated by Cajal, his peculiar life, self-absorption, intelligence, humility, and suffering, and in pursuing them so rigorously he gives his book an epic quality. Cajal wrote:

For the union of two minds to occur and generate fruitful results through a book, the reader must become fully absorbed in what the master has written, must penetrate its meaning fully, and finally must develop an affection for the author.

All of this applies to Ehrlich and The Brain in Search of Itself.

By Cajal’s time, it had long been believed that ringing a church bell during a storm would keep lightning from striking the church steeple. Cajal saw a lightning strike as a boy, and in Spark: The Life of Electricity and the Electricity of Life, Timothy Jorgensen quotes from his autobiography:

A voice coming from among the crowd called our attention to the strange, blackish figure hanging on the railing of the bell tower. In fact, there, beneath the bell, enveloped in dense smoke, his head hanging over the wall lifeless, lay the poor priest who had thought that he would be able to ward off the threatening danger by the imprudent tolling of the bell. Several men climbed up to help him and found him with his clothes on fire and with a terrible wound on his neck from which he died a few days later. The bolt had passed through him, mutilating him horribly.

Between 1753 and 1786, Jorgensen writes, 386 churches in France were hit by lightning, and 103 bell ringers were electrocuted. Cajal’s experience changed his thinking, Jorgensen says: “Afterward, he saw Mother Nature as fickle and sometimes extremely cruel.”

Jorgensen, a professor of radiation medicine at Georgetown University and the author of Strange Glow: The Story of Radiation, is interested in the ways that electricity operates in the body and in how it figures in ancient and modern medicine. The Romans applied shocks to patients from an electric fish called a torpedo fish to cure headaches, much as electric brain-stimulation techniques now treat Parkinson’s disease. It is possible that the letter Cajal received from the man who invented the brain-ventilating hat was written by August Toepler, the creator of something called the Toepler Influence Machine. Jorgensen tries one from 1900, which was then “considered state-of-the-art medical therapy.” It has a headpiece, and when the machine is turned on he feels as if a breeze is coming down on him from a ceiling fan. The treatment was often called “an electric head bath.” It was meant for headaches and bad thoughts, and how many treatments a person received depended on whether the headaches and bad thoughts went away.

John Wesley, the eighteenth-century cleric who began the revival movement that became the Methodist Church, believed that electricity could cure disease, especially nervous diseases. In The Desideratum: Or, Electricity Made Plain and Useful, he wrote that electricity could be a “rarely failing remedy, in the nervous cases of every kind (Palsies excepted).” Wesley thought that electricity was a fluid that fueled the nervous system and was the cause of motion and the sustainer of life throughout the animal and vegetable kingdoms. Jorgensen writes that he “deserves credit for being among the first to link electrical science with neuroscience.”

A thought is a passage of electrical impulses from one nerve ending to another. So is a movement, whether intentional or automatic, such as a heartbeat. The flow of electricity within us is caused by reactions among substances such as sodium, potassium, calcium, and magnesium and is so essential to our ability to move and to think and respond that when it is decisively interrupted, we die. Eating blowfish that hasn’t been properly cleaned of the toxin contained in the fish’s organs is deadly, Jorgensen writes, because the toxin, called tetrodotoxin, halts the passage of electrical signals: “Every bodily organ that depends upon those signals fails,” and the body that contains them dies.

Jorgensen writes about two approaches to brain theory: reductionist and antireductionist, neither of which is presently vulnerable to being overthrown the way Cajal overthrew reticular theory. Reductionist theory states that the smaller elements of the brain explain the more complex object, as if the brain were a type of computer, and that by studying how the senses work—how the eye transfers an image to the brain, for example—we will understand how the brain operates. Antireductionists believe that reductionist thinking overlooks what are called emergent properties, ones that arise “as a system functions and that cannot be predicted” simply from the workings of its parts. Consciousness is regarded as an emergent property, and so is sleep. Reductionist theory seems to have no explanation for these occurrences or how the brain controls behavior—“why, when the eyes see flames, the nose smells smoke, and the ears hear an alarm, the legs then get the body out of the building as fast as possible,” Jorgensen writes.

Jorgensen also includes material about pacemakers, electric eels, zombies, and epilepsy, which he calls “an electrical storm in the brain”; about the ways electricity can kill you—how lightning strikes and electric chairs work, for example; and how electricity can do peculiar things such as make the muscles of dead people move. By shocking victims of the guillotine, the Italian scientist Giovanni Aldini made them sit upright. Jorgensen speculates, as others have, that Mary Shelley drew indirectly on this phenomenon in Frankenstein.

Benjamin Franklin, who is often inaccurately said to have discovered electricity, once shocked himself while trying to electrocute a turkey. Franklin believed that “birds kill’d in this manner eat uncommonly tender,” although modern poultry research, Jorgensen says, appears to indicate that the flesh of birds killed by electricity might actually be tougher. Franklin’s testimony is one of the earliest accounts of what it feels like to touch the wrong wire. “I have lately made an experiment in electricity that I desire never to repeat,” he wrote to his brother. Witnesses told him that “the flash was very great, and the crack as loud as a pistol; yet, my senses being instantly gone, I neither saw the one nor heard the other.” Of the shock itself, he wrote that he felt “what I know not how to describe—a universal blow through my whole body from my head to my foot, which seemed within as well as without; after which the first thing I took note of was a violent, quick shaking of my body.” As a boy I once shocked myself severely by plugging in a light for my fish tank while my hands were wet. The current that traveled up my arm seemed to make its own path. When it was over, I thought, I’m still here.

Whereas Cajal witnessed the fatal effects of electricity in nature, Jorgensen describes mechanical ones. The first man to die in the electric chair, William Kemmler, a grocer who killed his girlfriend with a hatchet, died on August 6, 1890, in Auburn Prison in upstate New York. After the current had been sent through him for ten seconds, and he was being removed from the chair, he appeared to gasp, so they put him back in the chair and shocked him again, this time for several minutes, until, a reporter for the New York Herald wrote, “the room was filled with the odor of burning flesh and strong men fainted and fell like logs upon the floor.” It seems a hard road to have taken to the afterlife.