Walter Cannon

The word

Walter Cannon named the force that holds a body steady

Walter Bradford Cannon coined the word homeostasis in 1926, and he meant it as an engineering claim rather than a poetic one. Born on 19 October 1871 in Prairie du Chien, Wisconsin, he took his Harvard MD in 1900 and held the George Higginson Chair of Physiology at Harvard from 1906 until 1942, thirty-six years at the head of one department. The word first appeared in print in a French volume of tributes to Charles Richet, edited by Auguste Pettit, in a short paper running from page 91 to page 93. Its full technical statement came in 1929, in Organization for Physiological Homeostasis, Physiological Reviews, volume 9, pages 399 to 431 (Cannon 1929). It reached a general readership in 1932 in The Wisdom of the Body (Cannon 1932).

Ask what a name buys you. A name gathers scattered observations into one object that can be argued about, tested and taught. Before Cannon, the steadiness of blood sugar, blood calcium, blood oxygen, water content and body temperature sat in separate laboratories as separate curiosities. After Cannon they were one problem with one word attached to it. That is the entire function of a good technical term, and it is why the story of tone cannot skip this man. Tone is a claim about a regulated state. Cannon is the person who made regulated states respectable.

The inheritance

Claude Bernard supplied the observation and Cannon supplied the machinery

Cannon did not discover the internal environment. Claude Bernard did, and Cannon credited him at every opportunity. Bernard's Leçons sur les phénomènes de la vie communs aux animaux et aux végétaux of 1878 carries the sentence every physiologist knows: la fixité du milieu intérieur est la condition de la vie libre, indépendante (Bernard 1878). English renderings differ from translator to translator, which is worth stating plainly rather than pretending one version is authoritative. The sense holds across all of them. A creature is free to roam a hostile world only because it carries a private, defended sea inside itself.

Bernard described the constancy. He did not describe its defense. That is the gap Cannon walked into. Fixity was the wrong noun, because fixity implies a value held still by clamps, and nothing in a living body is held still by clamps. Blood sugar moves all day. Body temperature moves through the night. Calcium, sodium, pH and blood pressure all oscillate inside narrow bands. Cannon's insight was that the narrowness of the band, not the stillness of the value, is the achievement. Ask what that commits you to. If constancy is an achievement, then something is spending energy to achieve it, and that something can be found, measured and taken away to see what happens.

1896

The career opened with a goose, a bismuth capsule and a Roentgen tube

Cannon's first experiment made an invisible internal rhythm visible, and everything he did afterwards carries that signature. In December 1896, as a first year medical student barely a year after Wilhelm Roentgen announced his rays, Cannon fed bismuth subnitrate to a goose and watched the swallowed material travel down the throat under the new radiation. He demonstrated the method to the American Physiological Society that same month. His first paper, on the movements of the stomach studied by means of the Roentgen rays, appeared in the opening volume of the American Journal of Physiology in 1898, when he was twenty-six (Cannon 1898).

Notice the method. He did not ask the goose how it felt. He did not open the goose. He introduced a marker that made an ordinary internal process legible from outside, and then he watched. Anyone working with tone should respect that move, because tone has the same problem. The state of a nervous system is not directly visible. It becomes legible only through markers: tissue tension under a hand, breath rhythm, pupil, skin, posture, and the speed at which a body settles after being disturbed. Cannon's goose is the founding precedent for reading a hidden state through an honest external sign.

Emotion in the viscera

Cannon showed that a feeling can stop a stomach, and he showed it in millilitres

Bodily Changes in Pain, Hunger, Fear and Rage, published by D. Appleton in 1915, carried the subtitle An Account of Recent Researches into the Function of Emotional Excitement (Cannon 1915). It is the book in which emotion became a measurable physiological variable. The figures are still startling. A dog under quiet observation produced 66.7 cubic centimetres of gastric juice across twenty minutes. After emotional disturbance the same measurement fell to 9 cubic centimetres. Adrenin acted on a length of intestinal muscle at a dilution of one part in twenty million, and a sensitized segment responded at one part in two hundred million. Chapter five of the book is titled The Increase of Blood Sugar in Pain and Great Emotion.

Ask what that commits you to. If a frightened animal secretes roughly a seventh of the digestive fluid a calm animal secretes, then emotional state is not a commentary running alongside physiology. Emotional state is physiology, reported in cubic centimetres. Cannon closed the distance between the felt and the measurable from the measurable side, which is the only side that convinces a skeptic. Much of what the twentieth century learned about stress, digestion, immunity and pain runs back through those numbers.

The emergency function

Fight or flight began as a question about two small glands

Cannon's own heading was the emergency function. His 1914 paper in the American Journal of Physiology was titled The Emergency Function of the Adrenal Medulla in Pain and the Major Emotions (Cannon 1914), and the argument was that one sympathetic and adrenal discharge reorganizes the whole animal at once. Heart rate rises. Blood sugar rises. Blood leaves the gut and reaches the working muscles. Clotting time shortens. Digestion stops. None of these is a separate reflex firing on its own account. They are one command executed across many tissues, and Cannon was the first to insist that the coordination itself was the finding.

Two corrections belong here. The compact phrase fight or flight is the wording that survived him and it belongs to this line of work, but the later four part list that adds freeze and fawn comes from literatures written decades afterwards and should not be placed in Cannon's mouth. Second, the emergency response is not the opposite of homeostasis. Cannon was explicit that the two belong to one system, which is the point of the passage below. Arousal is not regulation failing. Arousal is regulation moving ahead of a load it expects.

Not stagnation

Cannon chose homeostasis over equilibrium on purpose

The word is built from the Greek homoios, meaning like or similar, joined to stasis, meaning standing or position. Cannon chose homoios rather than homos, which means same, and that single choice carries the whole concept. He also refused the obvious alternative. Equilibrium already had an exact meaning for relatively simple physico-chemical states in closed systems where known forces are balanced. A living body is not a closed system and its forces are not simply balanced. The phenomenon needed its own word, so he built one.

The definitional passage varies slightly between the 1932 first edition, the enlarged edition of 1939 and the 1929 journal statement, mostly in punctuation and in whether the line reads so complex and so peculiar or so complex and peculiar. The substance never moves. Anyone who uses homeostasis to mean unchanging is using it against the explicit instruction of the man who made the word. Ask what that commits you to. If a steady state is a varying state held inside a band, then health is a property of the band and of the return, not of any single number read once.

The postulates

Cannon wrote rules that any steady state must obey

The 1929 paper set out a numbered series of postulates (Cannon 1929), and they read less like classical physiology than like control engineering written twenty years early. Constancy in an open system is itself evidence that agencies are acting to maintain it. If a state holds steady, it holds because any drift is automatically met by an increase in the effectiveness of whatever resists the drift. A factor that shifts a state in one direction does not, at the same point, also shift it in the other. Agents that oppose one another in one region of the body may cooperate in another. A regulating system may be assembled from several factors acting together or in sequence.

The last postulate is the working instruction. Where a factor is known that can shift a homeostatic state in one direction, it is reasonable to look for automatic control of that factor, or for a factor with an opposing effect. That is a research program in one sentence, and it is also a clinical instinct. When a body is drifting, do not only ask what is pushing it. Ask what should be pushing back and is not.

The borrowed title

The phrase on Cannon's cover belonged to Ernest Starling first

The wisdom of the body was not Cannon's phrase. Ernest Henry Starling delivered the Harveian Oration before the Royal College of Physicians of London on St Luke's Day 1923 under exactly that title, nine years before Cannon's book appeared (Starling 1923). Starling is the man who coined the word hormone in 1905, and in that same oration he set out the classical account of how a hormone works: manufactured by one group of cells, released into the blood, carried to every part of the body, yet provoking definite reactions in only one or a limited number of distant organs.

This matters for more than credit. Starling's oration and Cannon's book are two halves of a single idea arriving in two countries within a decade. Starling described chemical messengers reaching distant tissues through the blood. Cannon described nervous and adrenal control holding the whole internal sea inside its limits. Between them they replaced a body made of organs with a body made of communication. That is the shift the tone model inherits, and it is why a tone reading is never a reading of one part.

The handoff

Cannon's regulation became the general science of control

The line from Cannon to feedback theory runs through one man. Arturo Rosenblueth worked with Cannon at Harvard for years, and the two published Autonomic Neuro-Effector Systems in 1937 and The Supersensitivity of Denervated Structures: A Law of Denervation in 1949, the second appearing after Cannon's death. In 1943 Rosenblueth published Behavior, Purpose and Teleology with Norbert Wiener and Julian Bigelow in Philosophy of Science, volume 10, pages 18 to 24 (Rosenblueth and Wiener 1943). Five years later Wiener published Cybernetics, and the vocabulary of negative feedback, gain, set point and oscillation entered general use (Wiener 1948).

Ask where that vocabulary came from. It came from a physiologist watching a body defend its own chemistry. Words such as feedback, regulation, damping, gain and instability are not borrowed metaphors when they are applied to a nervous system. They are being returned to the place they were taken from. That is worth saying clearly, because tone language leans on those words constantly and has every right to use them with a clean conscience.

The honest limits

Where Cannon stops and where this reading begins

Cannon measured blood, secretions, pressures, sugar and nerve discharge. He did not measure tissue tension, and he never proposed anything resembling tone as this library uses the word. His theory of emotion, developed with Philip Bard and published in the American Journal of Psychology in 1927 across pages 106 to 124 (Cannon 1927), placed emotional experience in central pathways rather than in the returning report from the viscera, and it remains contested. His 1942 paper on so called voodoo death, in American Anthropologist, volume 44, pages 169 to 181 (Cannon 1942), was offered as a hypothesis built on second hand ethnographic reports, and it should still be read as a hypothesis. He was never awarded a Nobel Prize.

The extension this library makes is one step, and it deserves naming rather than smuggling. Cannon showed that the body defends a set of chemical and circulatory states through nervous control. This library holds that the same nervous control expresses itself mechanically, as tissue tension, at every scale from a vessel wall to a whole standing posture, and that this tension can be read by a trained hand. Cannon did not say that. He made it sayable, which is a different and larger service.

Cannon and the model

Cannon named the defense of the internal environment, and the model names what mounts it

Cannon named the defense. Claude Bernard had established that the body holds its internal environment constant, and in 1926 Cannon gave the active defense of that constancy a word. The Unified Model of Tone begins from what medicine then did with the word. Medicine accepts that the body holds dozens of variables inside narrow healthy ranges: blood pressure, core temperature, blood pH, glucose, heart rate and more. Health is the body keeping each of them in its window. Disease is any of them drifting out and failing to return. What no one has claimed as one system is the property the body adjusts to move them. That property is tone.

Fight or flight is sympathetic tone under an older name. Cannon's 1914 paper on the emergency function of the adrenal medulla described one discharge reorganizing the whole animal at once. It lifted heart rate and blood sugar together, moved blood from the gut to the working muscles, shortened clotting time and stopped digestion. The model reads that list as one quantity moving. The autonomic nervous system runs on two opposing tones, a sympathetic tone that accelerates the body and a vagal tone that restrains it. When sympathetic tone outweighs vagal tone, heart rate, blood pressure and blood glucose climb. When vagal tone outweighs sympathetic, they fall. Cannon measured the climb. The model names the balance that produced it.

Health is not a fixed setting of that balance. Health is the ability to move the balance to wherever the moment demands, which is why Cannon refused to let his own word mean stillness. He built it from homoios, meaning like or similar, rather than homos, meaning same, so that it would describe a value held inside a band. He was equally explicit that the emergency response belonged to the same system as the steady state, preparatory to exertion rather than a breakdown of it. Tone works the same way one level up. Tone inside its healthy range is health, because the range is what keeps a body free to adapt. Tone that drifts outside that range and cannot return is what shows up as illness.

Say plainly where the record stops. Cannon measured blood sugar, gastric secretion, adrenal discharge and nerve traffic, and he set out the postulates any defended state must obey. He never claimed that the many defended values are moved by one property, and he never used the word tone in the sense this library uses it. That claim is the model's own, and it is testable in the ordinary way. The model holds that autonomic regulation, tissue tension, cortical excitability and the rest are readings of one variable, so showing those measures load on one common factor in the same people establishes it. The generation after Cannon, beginning with Hans Selye, asked what happens when the defense runs without pause. Cannon named the defense. The model names what the body adjusts to mount it.

What the record shows

The defense of the internal environment in seven dated findings

• December 1896. As a first year medical student, Cannon fed bismuth subnitrate to a goose and watched the swallowed material travel under Roentgen rays. His first paper on the movements of the stomach appeared in the opening volume of the American Journal of Physiology in 1898, when he was twenty-six (Cannon 1898).
• 1914. The Emergency Function of the Adrenal Medulla in Pain and the Major Emotions, in the American Journal of Physiology, argued that one sympathetic and adrenal discharge reorganizes the whole animal at once. The coordination itself was the finding (Cannon 1914).
• 66.7 to 9 cubic centimetres. In Bodily Changes in Pain, Hunger, Fear and Rage, 1915, a dog under quiet observation produced 66.7 cubic centimetres of gastric juice in twenty minutes, and 9 after emotional disturbance. Adrenin acted on intestinal muscle at one part in twenty million (Cannon 1915).
• 1926. The word homeostasis first appeared in print in a French volume of tributes to Charles Richet, edited by Auguste Pettit, in a short paper running from page 91 to page 93.
• 1929. Organization for Physiological Homeostasis, Physiological Reviews volume 9, pages 399 to 431, set out the postulates. Constancy in an open system is itself evidence that agencies are acting to maintain it (Cannon 1929).
• 1923. Ernest Starling delivered his Harveian Oration under the title The Wisdom of the Body, nine years before Cannon's book of that name (Starling 1923). Starling coined the word hormone in 1905.
• 1943 to 1948. Arturo Rosenblueth, Norbert Wiener and Julian Bigelow published Behavior, Purpose and Teleology in Philosophy of Science volume 10, pages 18 to 24 (Rosenblueth and Wiener 1943). Wiener's Cybernetics followed in 1948, carrying feedback, gain and set point into general use.