Before the era of anesthetics, walking to the oper­ating room resembled “going to a hanging,” in the words of one surgeon. So imagine what sur­gery was like for the hapless ­patient.

The changes that accompanied the advent of anesthetics in the 1840s—particularly in Britain and the United States—are the focus of Stephanie Snow’s 

. Anesthetics affected the practice and evolution of general surgery, dentistry, and military medicine, and altered childbirth. They also brought about social changes, as people came to understand that experiencing physical pain was not crucial to a moral life; indeed, sometimes a pain was just a pain.

The earliest anesthetics—ether, chloroform, laughing gas—had distinctive strengths, weak­nesses, and uses. Dentists favored laughing gas—a ­short-­acting agent—for their quick procedures. Ether required careful titration by a specialist. Chloroform was the easiest to use but also the most commonly associated with overdosing, addiction, and ­death.

Over many decades, the merits of anesthetics on the battlefield remained controversial. Were they too flammable for use near gunfire? Might their depressant effects hamper recovery in the severely traumatized? “The smart of the knife is a powerful stimulant and it is much better to hear a man bawl lustily than to see him sink silently into the grave,” wrote the British chief medical officer of the Cri­mean War in 1854, but others believed there were limits to how much trauma one shocked soldier could ­endure.

In the United States during the Civil War, anesthetics had a second use. Soldiers suspected of ma­lingering were lightly anesthetized and then as­signed tasks. Those who performed successfully were dispatched back into battle. Not until the 1880s, Snow notes, did the “concept of traumatic or ­post-­traumatic neurosis become established as a medical category of disease,” accounting for soldiers who were physically able but psychologically ­scarred.

The elite revered anesthetics. Charles Darwin ­self-­experimented with chloroform and in 1850 gave it to his wife, Emma, during labor, writing that he “kept her in a state of insensibility of 1 & 1/2 hours & she knew nothing from first pain till she heard that the child was born.” Physician John Snow, a central figure in the book and a distant relative of the author, administered chloroform to Queen Victoria during the births of her eighth and ninth children in the 1850s, giving rise to debate in 

 and other publications between those who found the use of anesthetics for normal birth dangerous and ­irresponsible and those who embraced the practice.

Anesthetic compounds were initially easy to purchase. Asthma and toothache sufferers ­self-­administered them. Muggers and robbers used them to stun their victims. Individuals caught in compromising situations claimed to have been etherized to “account for being in disreputable places and company.”

In the 20th century, “the needle . . . replaced the mask,” Snow writes, and researchers developed many new compounds with single effects—analgesia, amnesia, muscle relaxation, sedation—and ­fine-­tuned their uses, making surgeries and dentistry ­safer.

The story of anesthesia is fascinating, a mix of surprising social consequences, engaging philo­sophical debates, curious personalities, experi­ments gone right and wrong. But Snow, a re­searcher at the Center for the History of Science, Technology, and Medicine at the University of Manchester, is too often a stiff stylist, and frequent insider asides and digressions detract from many of the interesting tales she ­tells.

Today anesthesia is integral to Western medi­cine, though some—myself included—elect to forgo it when we can (in the dentist’s chair; during childbirth), realizing that every drug has unpre­dictable side effects. Others, of course, take anes­thetics for the side effects. The ­19th-­century transcendentalists, for example, saw ­self-­exper­i­­mentation as a path to spiritual enlighten­ment. “You expand like a seed . . .” wrote Henry David Thoreau. “You exist . . . like a tree in the winter. If you have an inclination to travel, take the ether; you go beyond the furthest star.”

 teaches bioethics at Haverford College and writing at Johns Hopkins University, in the arts and sciences graduate program. She is a regular commentator on NPR’s

 Baby at Risk: The Uncertain Legacies of Medical Miracles for Babies, Families, and Society (2006).

Blessed Days of Anaesthesia: How Anaesthetics Changed the World

 by Stephan J. Snow, Oxford University Press, 226 pp, 2008.

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Ruth Levy Guyer on the history of anesthesia.