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What Is the Brain? Wiener believes that the human brain resembles a computing machineand vice versa. Dr. Warren McCulloch, professor of psychiatry at the University of Illinois College of Medicine, goes further: he says that the brain is actually a computer, and very like computers built by men.
The brain's essential parts, says McCulloch, are "neurons" (nerve cells). There are about 10 billion of them, and they are living electrical relays, comparable to the relays and vacuum tubes in the machines. The neurons are intricately connected by fine, often branching fibers, so the whole brain is a lacelike network of relays and conductors.
Along the brain's interlaced "wires" run swift electrical pulses generated by the neurons, which serve as living batteries. When a pulse runs out along a fiber, it comes eventually to a complicated little structure called a "synapse" that connects with a fiber of another nerve cell. The pulse may pass through a synapse or it may not pass; no one knows why.
When a pulse or several of them do pass, the second neuron "fires," sending out a pulse of its own. Out of such single pulsesbillions of them flashing in zigzags and rivers through the thinking brainhuman thoughts and decisions are built.
$300 an Hour. Practical computermen, some of whom deplore McCulloch's analogies, agree with him on one point: that the machines need better memories. The machines are already quicker than the brain: their vacuum tubes act 1 ,000 times faster than neurons. But their poor memories (rudimentary compared to the brain's) limit their thinking abilities. The punched tapes and cards that some of them spew out are not real internal memories, since they cannot be consulted quickly. They are more like reference libraries.
Harvard's Mark III, soon to be delivered to the Navy, has the best memory of any machine so far. Its memory is housed in fast-spinning aluminum cylinders whose surfaces are coated with black magnetic material (see cut). On the black surfaces, its electrical signals print long numbers in the form of magnetized dots. When the cylinder makes its next turn, the dots can be read off again in a small fraction of a second. They can be destroyed, replaced with other numbers or retained permanently.
Its quick "magnetic memory" is what makes Mark III an effective computer. Professor Aiken is so well pleased with it that Mark IV, which Harvard is building for the Air Force, will use the same system. Mark IV will "live" (Aiken, the conservative, says "live") at Harvard permanently, and part of its time will be available to non-military users. Scientists will cheer this news. Nearly all the existing computers do nothing but military work. Only the big I.B.M. machine on Manhattan's Madison Avenue is open to nongovernment scientists, and I.B.M. charges $300 an hour for its services.
New, radical memory devices are coming along fast. Among the more promising are "memory tubes." One type, developed by Professor F. C. Williams of Manchester, England, uses a thin beam of electrons to print meaningful dot-numbers on its flat end. They can be used in the machine's calculations and erased electrically in a few millionths of a second.