The correspondences between technical apparatus and living organisms are particularly striking. When the temperature rises too much for the refrigerator's comfort, and its thermostat therefore switches on its motor to cool it down - that is a technical controlling process which lies within the sphere of cybernetics. When it gets too warm for people and they sweat, so that their body temperature is brought down by the evaporation of their perspiration, that is a process of control in a living organism. The correspondence between the mechanism of the refrigerator and that of the sweating human is one of the departments in which cybernetics is very much interested.
If a moth - a real live one - creeps towards the light, using the incidence of the light rays on its eyes as a guiding line, and if on the other hand Professor Wiener's artificial moth behaves in just the same way and allows its mechanism to propel it towards a source of fight - that is a matter for the cyberneticist.
If a primitively organized animal looks between sunlight and shadow for the spot with the temperature that suits it best; if a price regulates itself according to supply and demand; if an electric oscillatory circuit sets itself at a certain value by a closed loop feed-back control - that too belongs to the realm of cybernetics.
The electronic computers are practically ideal "cybernetic models," although their designers in the beginning - until Norbert Wiener began to think about the matter - failed to notice the fact, or if they did, thought it was unimportant The capabilities of these electronic automata correspond entirely to the spheres which Professor Steinbuch called the "elements of cybernetics": they are capable of control-processes, they concern themselves with the transmission of information and particularly with the processing of information.
So it is not really astonishing that cybernetics can find many connections between computers and organisms. There is thus a similarity between the electric wires of a computer and organic - we might as well say human - nerve fibres. Nerve tracts, as the biologists have ascertained, are basically nothing but electrical conductors. They consist of chains of minute galvanic cells which can transmit electrical impulses much as a chain of workers used to pass bricks along to the bricklayer. There is a theory - not an undisputed one, but at any rate unrefuted - according to which the small nerve cells can exist in only two states: they can be electrically charged, or uncharged. If this theory is correct, the language of our nerves is simply "yes" or "no" - they work digitally, just as most electronic computers do. The picture of the flower transmitted from the eye to the brain, the sensation of another hand held in your own, the pain you feel at the dentist's, your thoughts - all these, then, are conducted by a system similar to that which governs the flow of information in the wires of a computer.
The cells of the brain and the spinal cord are also composed (this much is certain) of such tiny electrically reacting units, and our present knowledge leads us to suppose that they react in the same way as the circuits in the arithmetic unit of an automatic calculator. Of course, the circuits in the brain must be far more complicated than those in the most sophisticated computer. It is fairly certain that the brain does not make any fine distinctions between cells of the arithmetic unit, storage cells and conducting cells. It uses all of them with sublime indifference, now for one purpose, now for another.