Galen — The Book That Said Go and Look

The previous three articles concerned the sky, the air and light. Being wrong about them killed nobody. This one is different: a theory whose wrong values were applied directly to bodies.

What comes out of a body

It begins with Hippocrates, whose achievement was to make illness a matter of the body rather than of divine punishment. Medicine starts there.

What about the body, then? The answer came from observation: look at what comes out of a sick one.

1. A festering wound gives a yellowish fluid, as does a running nose — phlegm.
2. A cut gives something red — blood.
3. Vomiting brings up something bitter and yellow — yellow bile.
4. Bleeding in the gut turns the stool black — black bile.

A window briefly open

In third-century-BC Alexandria the dissection of human bodies was permitted for a short period — a rare opening in human history.

Herophilus distinguished nerves from tendons, separated sensory from motor nerves, and placed the intellect in the brain rather than the heart. He could know these things because he had looked.

The window soon closed. In Rome, dissecting a human body was forbidden.

Galen was not lazy

This is the heart of it. A theory that stood for fourteen centuries would be a dull story if it were the product of idleness. It was the opposite.

As physician to gladiators Galen saw into bodies through open wounds. And he experimented.

1. He found and tied a nerve in the neck of a living pig. It thrashed on but its squealing stopped — the voice is governed by a nerve descending from the brain.
2. He cut the spinal cord at different heights. What was paralysed depended on where he cut — nerves run down the cord.
3. He tied an artery in two places and opened the stretch between. Inside was blood, not air, overturning a widely held belief.
4. He tied off the tube from a kidney and the side above it swelled — urine is made in the kidney and passes down.

And he never opened a human

Roman law forbade it. What he opened were Barbary apes, pigs, dogs and bears.

So his anatomy contains structures that people do not have.

A little further in

What happened in between

The intervening centuries are often described as empty. They were not. The Islamic world did not merely preserve Galen; it tested him.

In tenth-century Persia al-Razi wrote a book titled Doubts about Galen, setting down point by point where his own patients differed from Galen's descriptions — and adding that writing this way was surely what Galen himself would have wanted.

The trouble grew elsewhere: in the universities of Europe, Galen became the textbook.

What Vesalius did

In 1543 — the year of Copernicus's book — a twenty-eight-year-old named Vesalius published On the Fabric of the Human Body.

He invented no instrument and proposed no new theory. What he did was pick up the knife himself.

And he found more than two hundred places where the book and the body differed. Of the pores in the septum he wrote that however hard he looked, no such passage could be found.

His most important finding was not any single error. It was that what Galen had described was not a human body but an ape's.

Two invisible things

The decisive blow came from Harvey in 1628, and his weapon was not observation but arithmetic.

Measure what leaves the heart in one beat and multiply by a day's beats: you get many times the weight of the body. No liver can manufacture that daily. So the same blood must be going round.

Harvey had a gap of his own. Something had to connect the arteries to the veins, and he could not see it; there were no microscopes.

But the bleeding stayed

The treatment outlived the theory. Harvey established circulation in 1628; Washington was bled to death 171 years later.

Why did it last? Because it appeared to work.

1. Bleeding brings the fever down and slows the pulse. It genuinely does — there is less blood.
2. If the patient recovers, the bleeding worked.
3. If the patient dies, they came too late or were too far gone.
4. Whatever happens, the theory is safe.

What it left

Bloodletting did not vanish either. For conditions in which the blood grows too thick, or iron accumulates in the body, drawing blood remains a standard treatment. Only the reason has changed.

1. 400 BCHippocrates — disease becomes a matter of the body
2. 280 BCHerophilus — dissects humans at Alexandria
3. 170Galen — experiments on animals, forbidden to open humans
4. 910Al-Razi — Doubts about Galen
5. 1543Vesalius — takes up the knife and corrects two hundred points
6. 1628Harvey — proves circulation by arithmetic
7. 1661Malpighi — sees the capillaries
8. 1799Washington — dies after repeated bleeding
9. 1828Pierre Louis — shows by counting that bleeding does not help

The question that remainsGalen told his readers to go and look, and they read the sentence instead. Of the things we hold to be settled and pass over, how many do we know who last checked, and when?