How does one cell “know” what the others are doing and therefore act in concert and thereby register a sensation or commit the nervous system to a response, an action, a thought? If the answer wasn’t in the cells, those solitary hubs, then it had to be elsewhere.
And the only elsewhere there was, was the fibers. Thanks to Gerlach’s staining method, neuroanatomists now found that the fibers extend from the central nerve cells only into the white matter of the brain and spinal cord, never the gray. But there the trail went cold. The meshwork was still too intricate for anyone to trace the paths of all the fibers from a single cell to the point where the fibers terminate. And so yet another technical innovation needed to be invented, and so yet another one was. In 1873—the same year that Freud entered the University of Vienna as a medical student—Camillo Golgi, an Italian physician, developed a superior staining method that in effect isolated the fibers in the same way that Gerlach’s had isolated the cells. Even so, researchers still couldn’t find one point of connection between the fibers of two different cells. Golgi himself thought he found one in the 1880s, but his sample was inconclusive. Still, in order to do what central nerve cells do, which is pass along impulses to one another, both prevailing theory and common sense dictated that the fibers of neighboring cells must connect, somewhere.
Not until 1889 did the Spanish histologist Santiago Ramón y Cajal discover the truth: They don’t, anywhere. This, then, was the basic unit of the brain, what the German anatomist Wilhelm Waldeyer two years later would name the neuron: each central nerve cell and its own fibers, existing apart from—that is, not connecting to—any other central nerve cells and their own fibers. But if even the least wisp of a fiber—a fibril—doesn’t connect, what does it do? It contacts, Ramón y Cajal explained. It reaches out, under the excitation of an impulse, to touch the neighboring fibril or cell, and then, when the excitation has relaxed, it retracts to its previous state of isolation. “A connection with a fiber network,” Waldeyer wrote, “or an origin from such a network, does not take place.”
Although at first the “neuron doctrine,” as Waldeyer christened it, might have seemed to contradict common sense, upon reflection the idea that communication between individual neurons was not continuous but intermittent actually went a long way toward a possible explanation of several otherwise inexplicable mental phenomena, such as the isolation of ideas, the creation of new associations, the temporary inability to remember a familiar fact, the confusion of memories. These were the phenomena, anyway, that Freud had been confronting in his private practice, where he found himself listening at length to hysterics, and wondering how to represent their worries and cures within the webwork of cells and fibers he remembered from his years of neuroanatomy.
“I am so deep in the ‘Psychology for Neurologists’ that it quite consumes me, till I have to break off overworked,” Freud wrote to a friend in April 1895. “I have never been so intensely preoccupied by anything.” By now Freud had embarked on a second career. From 1873 to 1885, first as a medical student and then as a medical researcher, he’d devoted himself to an examination of the nervous system—to research in neuroanatomy. In 1886, on the eve of his thirtieth birthday, he’d opened a private practice devoted to nervous disorders and, for the first time in his life, begun seeing patients, though he continued to conduct research on the side. After the development of the neuron theory, Freud would have had every reason to believe that if anyone were in a position to unite the psychical with the physical, it was he. He’d seen both sides. He’d studied both sides, immersing himself in the peculiar logic of each for long periods of time. He’d even written some tentative outlines to this effect over the past few years, in letters to his closest friend and constant correspondent, Wilhelm Fliess, a Berlin ear, nose, and throat doctor. Not until Freud could meet with Fliess personally late in the summer of 1895, however, and the two men could convene one of their days-long “congresses,” as Freud liked to call these occasional periods of intense and inspirational professional discussion, did he see the project whole.
Freud began composing the manuscript on the train ride from Berlin back home to Vienna that September. “I am writing so little to you only because I am writing so much for you,” Freud informed Fliess by letter on September 23. Barely two weeks later, on October 8, Freud mailed a draft to Fliess—a hundred or so handwritten pages in which he attempted to explain definitively the processes of the mind by describing exhaustively the mechanism of the brain that encases it.
And a mechanism it was. “The project,” Freud wrote, in the second sentence of the manuscript, “involves two principal ideas”: in essence, and in accord with Descartes’s philosophy and Newton’s physics, motion and matter. Freud’s principal idea number I was straightforward enough: that the workings of the brain are “subject to the general laws of motion”—that matter moves immediately adjacent matter with comprehensive cause-and-effect predictability. What contributed to Freud’s sense of urgency in composing this draft, however, was that he now knew what the “matter” was: “2. That it is to be assumed that the material particles in question are the neurons.” He based this assumption, as he made explicit several pages later, on “the knowledge of neurons which has been arrived at by modern histology.”
Yet even as he was passing the manuscript along to Fliess, Freud was starting to have his doubts. “I have been alternately proud and overjoyed and ashamed and miserable—until now, after an excess of mental torment, I apathetically tell myself: it does not yet, perhaps never will, hang together,” he wrote in the accompanying letter. “I am not succeeding with the mechanical elucidation; rather, I am inclined to listen to the quiet voice which tells me that my explanations are not yet adequate.”
In the weeks to come that inner voice softened briefly, then hardened again. “During one industrious night last week,” Freud wrote to Fliess on October 20, twelve days after posting the manuscript, “the barriers suddenly lifted, the veils dropped, and everything became transparent—from the details of the neuroses to the determinants of consciousness. Everything seemed to fall into place, the cogs meshed, I had the impression that the thing now really was a machine that shortly would function on its own.” On November 8, however, he reported that after other professional commitments had forced him to put the manuscript aside, he found he couldn’t stop thinking about it—specifically, he noted with regret, that “it required a lot of revision. At that moment,” he went on, “I rebelled against my tyrant. I felt overworked, irritated, confused, and incapable of mastering it all. So I flung it all aside. If you felt called on to form an opinion of those few sheets of paper that would justify my cry of joy at my victory, I am sorry, because you must have found it difficult.” Freud added that in another two months, after he’d fulfilled his obligations, “I may be able to get the whole thing clearer.” It was not to be. Only three weeks later he wrote to Fliess, “I no longer understand the state of mind in which I hatched the psychology; cannot conceive how I could have inflicted it on you. I believe you are still too polite; to me it appears to have been a kind of madness.”
Maybe so. Whatever it was, it was over now, as if a fever had broken. The problem that Freud had found himself confronting was larger than pathways of nerves, larger than the neuron itself—or, maybe, smaller. Either way, it was the same problem that had been haunting physiology since the inception of the modern era more than two centuries earlier: brain. To be precise, it was brain in opposition to what the motions of matter within the human cranium represent: mind, maybe.
For much of human history, such a distinction would have been secondary, at best. The far more important distinction, instead, would have been the one between two types of matter: terrestrial and celestial. Down here, as Aristotle had said, were the four elements—earth, air, fire, and water, either alone or in any number of combinations. Up there was one element—quintessence, a single perfect substance that constituted the moon, sun, planets and stars, as well as the spheres that carried them on their heavenly journeys. An Earth that itself traveled through the heavens, however, not only erased the crucial distinction between what was terrestrial and what was celestial but—as Descartes appreciated when he was merely a budding philosopher—presented a strong argument that everything
