The Brain in Search of Itself: Santiago Ramón y Cajal and the Story of the Neuron. By Benjamin Ehrlich. Farrar, Straus and Giroux; 464 pages; $35. To be published in Britain in April; £27.99
IN 1906 THE Nobel prize in physiology or medicine was shared by two scientists with irreconcilable views of the brain. At the ceremony, Camillo Golgi, an Italian anatomist and the elder of the pair, spoke first—and shocked the audience by slamming his rival’s theory. When the other laureate spoke, he described his scientific results, building a convincing case on facts. But Santiago Ramón y Cajal concluded with barbed sympathy for “this scientist who, in the last years of a life so well-filled”, had seen “his most elegant and original discoveries [treated] as errors”.
This was one of the founding events of modern neuroscience and is the central drama in Benjamin Ehrlich’s new biography of Cajal. Golgi had devised a staining technique, using silver nitrate, which allowed nervous tissue to be visualised in more detail than ever before. Cajal perfected the technique and claimed, on the basis of his observations through a microscope, that the nervous system—including the brain—was comprised of individual cells, or neurons. This went against the prevailing theory, supported by Golgi, which held that it consisted of a reticulum or continuous sheet of fibres. Cajal was right.
The “peasant genius”, as his friend and fellow histologist Charles Sherrington called him, lived out a scientific rags-to-riches story. He was born to a modest family in the remote Pyrenees of Aragon, at a time when Spain was a scientific backwater. By the time he died in 1934—having obliged British, French and German scientists to learn Spanish just to read his papers—he had almost single-handedly placed the country on the scientific map, in the process ensuring his own status as a national hero. Not bad for a delinquent who was forced to steal bones from graveyards to study anatomy in his youth.
What made that possible was a rare mix of scientific curiosity and artistic flair—and a wife, aptly named Silveria, whose faith in him never wavered. “Half of Cajal is his wife,” he liked to say. “The Texture of the Nervous System of Man and the Vertebrates”, his masterpiece of 1904, is a scientific classic; his drawings of neurons were prized as works of art. Cajal was blessed with a phenomenal visual memory and methodical rigour, but he had a Romantic soul. He saw himself as Don Quixote and Spanish science as his Dulcinea.
The father of the neuron, as he is often called, either introduced or popularised concepts that neuroscientists still debate, from the potential for nervous-system regeneration, to the influence of the chemical environment on the wiring of the embryonic brain, to the organ’s plasticity. All these phenomena, in his view, operated on the basic unit of the nerve cell. Cajal was a dyed-in-the-wool individualist—and if Mr Ehrlich is a trifle heavy on the comparisons between the microscopic world and Spanish politics, his larger point about the role of metaphor in science is important.
For ever since human beings first inquired into their own brains, they have fallen back on technological metaphors. It was the telegraph in Cajal’s day; now it is the computer. Neither is particularly realistic, but both capture aspects of the truth. Networks are a perennial theme and Golgi, who took a holistic view of the nervous system, saw them everywhere. Cajal was warier of them. But as neither ever saw into the spaces between neurons, they had to intuit what was or wasn’t there. Cajal imagined a gap, Golgi a web of filaments.
The metaphor invaded Cajal’s drawings. Despite his eye for details, he left out those he thought unimportant. He knew that intuition precedes observation, but his choices left him open to criticism and he had to defend his theory all his life. Today the reticulum is back, if in different form—the idea being that what counts in the nervous system is patterns of neuronal activity. Cajal might just about accept that, since his legacy, the neuron, is safe.