IF YOU CONCENTRATE on your breathing, just for a minute, you feel better.

It's the same with perspective. It's low-hanging fruit. Just a few minutes spent thinking about how far humanity has come — in engineering, music, social tolerance or medicine — reminds me that the enterprise of civilization has a momentum that my petty failures can't stop.

I'm working on the medicine bit now by reading the late Roy Porter's 1998 book "The Greatest Benefit to Mankind: A Medical History of Humanity." It's about 700 pages long, and every few pages I have to stop and rethink my understanding of the body. (About every hundred pages I fall asleep. Sorry, the late Mr. Porter.)

Did you know that surgeons used to operate as fast as they could, doing things like amputations in seconds or minutes? It wasn't just to keep a lid on the period that bacteria could get into the wound — for most of history we didn't know about bacteria. And it wasn't entirely to show off, either. Surgeons went really fast because they had no way to limit the patients' blood loss or pain. Which reminds me: scientists died testing out early anesthetics on themselves.

To give you some perspective on how deadly the past is: in 1750 the average Frenchman lived to be about 27 years old. And don't forget that babies and infants died way more than they do today, which pushes that average down. Today about a 1 percent childbirth mortality rate is common in first-world countries; 250 years ago it was 20-30 percent.

More folks died than were born in cities, and people just accepted that cities needed constant immigration to keep going. In a lot of cultures, though, people wouldn't let doctors or medical students dissect the corpses. Ancient physicians dissected dogs and made mistakes assuming that human anatomy worked the same way. And then new physicians and researchers came along and tried to say, "That's not how it is!" and their detractors said, "But Aristotle/Galen/other dead guy said so!"

(Yep, mostly guys. Did you know women weren't allowed into Harvard and Yale medical schools till after World War II?)

But students did eventually want to look at the pipes themselves. In Europe and Canada a few hundred years ago, body-snatchers broke the law by stealing fresh corpses from graveyards. Hilarious name for them: "resurrectionists." Imagine finding out your mom's grave had an empty coffin!

One hotel owner had a guest die and sold the corpse to a resurrectionist. The obvious question: why wait for people to die naturally? The team killed about a dozen people before getting caught.

Be careful what you incentivize!

There was a long period in the 18th and 19th centuries where researchers were making leaps and bounds in theoretical understanding, but it didn't much help patients. Regular doctors, not just scientists, had to understand that bloodletting didn't help and handwashing did; that took a while.

It's just astonishing, the things we take for granted. Vitamins were isolated less than a century ago. The first real blind clinical trial was in 1946, and it pointed to a cure for tuberculosis. Surgeons and doctors used to think of their professions as quite separate; the original Hippocratic oath banned surgery by doctors.

The Hippocratic oath also prohibited doctors from participating in certain euthanasia and abortion methods. (This is so unusual, according to what we know of ancient Greek beliefs, that it makes some historians think it was added later.) But the most surprising item in that old oath is the rule against teaching medicine to students unapproved by one's master.

That disorients me the most. People died of diseases we can now easily cure, and women had little say — I can try on that mindset like a too-small shoe. But I can't get being a miser with knowledge.

It's not just secrecy that stops innovation. It's narrowmindedness, too, the unintentional kind. There's some received wisdom that everyone believes because it's traditional.

Then someone new comes along and sees with new eyes and makes a new model for how the body works, and there's a flurry of new experimentation. Then that model calcifies and becomes the new received wisdom for a few hundred years, until the next revolution comes along.

I shared this brilliant insight with my husband. He reminded me that I had basically just reiterated the thesis of Thomas Kuhn's history of science, "The Structure of Scientific Revolutions," first published in 1962. I'd read it years ago. It's a luxury, isn't it, to get to read so many books that you've forgotten some? More perspective.

Sumana Harihareswara writes for Bay Area Living each week. You can write to her at sumana@crummy.com.