by David Zax

Tonsils, those oval-shaped masses of tissue in the back of your throat, have been the targets of surgeons from the earliest days of medicine. Around 1000 BC, doctors in India practiced partial tonsillectomies. In the days of Jesus, a Roman physician named Aulus Cornelius Celsus recorded performing tonsillectomies by holding on to the tonsils with “a blunt hook” and excising them. But even today, doctors don’t completely understand the function of tonsils. It’s believed that they help prevent infection in the respiratory and digestive tracts; however, the tonsils themselves are prone to infection because they have pitted surfaces that tend to capture food debris.

That tendency for infection led to a tonsillectomy boom in early 20th-century America. According to a longitudinal New York State study, two-thirds of males born between 1910 and 1929 no longer had tonsils by the age of 19. And most weren’t actually sick at the time of the surgery; their tonsils were removed as a precautionary measure. The trend continued, and by the middle of the century, between 1.5 million and 2 million tonsillectomies were being performed annually in the United States. The operation had turned into a rite of passage—a normal part of growing up.

One reason tonsillectomies became commonplace is because new antiseptic techniques and cleaner hospitals made the surgery less dangerous. Another reason has to do with something called the “focal theory of infection.”

Around 1910, a few prominent American physicians expressed their belief that infections in one part of the body could easily spread to the rest of the body, leading to systemic diseases. The theory posited that an unchecked infection could lead to arthritis, nephritis, mental illness, or other disorders. And because tonsils often became extremely inflamed, they were singled out for removal as a potential danger to the body as a whole.

Although there was little consensus on the focal theory of infection, the voices of a few influential clinicians carried the day. By 1915, the tonsillectomy had already become the most common surgical procedure in the United States—a reign that would last for half a century. Of course, not all doctors supported the surgery. In 1938, a British medical report called the operation a “ritual” with “no particular result.” Also, the procedure was by no means free of risk; thousands died every year due to complications from the operation. A letter in the journal Pediatrics in 1968 urged that the tonsillectomy itself be considered an “epidemic.”

By the 1970s, the rate of tonsillectomies finally began to decline, and today, only about 8 percent of the population undergoes the operation before reaching adulthood. Although there are still about 400,000 tonsillectomies performed in the United States each year, the surgery is no longer carried out on healthy people. Instead, it’s mostly used as a treatment for chronic tonsillitis and sleep apnea, for which it has proven quite effective. But for the first half of the 20th century, millions of people had their tonsils removed, and thousands died from it, for no particularly good reason.

This article originally appeared in mental_floss magazine. If you’re in a subscribing mood, here are the details. Got an iPad or another tablet device? We also offer digital subscriptions through Zinio.