Museum Blog

For our Health and Science Writing class, students had to pick a museum or exhibit they’d be interested in visiting and write a blog post for it. I chose the Dittrick Museum of Medical History at Case Western Reserve University and focused on the museum’s unique exhibit on contraceptive devices throughout history. Specifically, I wrote about thermometers—not particularly sexy, but fascinating when you realize how this simple device helped countless women take control of their health and reproductive abilities.

It’s Getting Hot in Here, So Don’t Take Off Your Clothes: Thermometers as Contraceptive Devices

Let’s be honest: Most adults would agree that sex is (usually) pretty fun. Getting pregnant when you’re not expecting it...not so much.

That probably explains why, ever since human beings realized that “knocking boots” leads to babies, we’ve been on the hunt for methods and tools that allow for sexual fulfillment without the side effect of unwanted pregnancies—many of which are on display in the Percy Skuy Collection and Gallery here at the Dittrick Medical History Museum. Long before modern contraceptive methods like birth control pills, implants, and condoms were invented, women were resorting to some truly bizarre ways of preventing pregnancy. For instance:

  • Egyptians were known to use crocodile poop to create their own cervical caps.

  • In the Middle Ages in Europe, women were advised to tie the testicles of a weasel to their thighs or around their necks during intercourse as a means against getting pregnant.

  • Chinese women would drink liquid mercury to prevent pregnancy.

Fortunately, a lot has changed over the last few centuries. Scientific advances allowed for more effective and less disgusting methods of birth control, so uterus-owners today can rely on hormones instead of reptile feces to prevent pregnancy.

But one method of birth control has stood the test of time. It’s not that glamorous, and it’s certainly less attention-grabbing than a pair of weasel testicles. In fact, it’s something most people have in their medicine cabinet at home—but it’s given thousands of women a measure of control over their bodies and lives.  

Introducing: The thermometer.

That’s right—this innocuous device has been essential for sexually active women for decades, enabling them to track their most fertile days and avoid unwanted or untimely pregnancies. Let’s take a look at this game-changing instrument and how it continues to be used today.

Invention of the Thermometer & Discovery of Body Temperature

Since the earliest days of medicine, healers and physicians recognized that an abnormal increase in temperature could indicate certain illnesses—but for many years, there were no ways to accurately measure the temperature of the human body. Some physicians would use their hands as a standard for estimating temperature, but it was hardly an accurate way to know how feverish a patient might be.  It makes sense, then, that many doctors and scientists throughout history pursued a way to accurately measure the temperature of the human body and track fluctuations from a set point.

Our modern thermometers today can thank Daniel Gabriel Fahrenheit for their creating their common ancestor, the mercury thermometer, in 1713.  If you recognize his name, it’s probably because he is also the father of the Fahrenheit temperature scale, created roughly ten years after the introduction of his mercury thermometer.  Fahrenheit’s scale was based on the freezing point of water (32 degrees) and the boiling point of water (212 degrees), with everything between divided into 180 equal parts.

Thanks to Fahrenheit, his thermometer, and his standardized scale, humanity finally found a measurement of a “normal” human body temperature: 98.6 degrees. Moving forward, physicians could use temperature as a diagnostic tool.

Thermometers and the Rhythm Method

While the base temperature of the human body was no longer a mystery, the cycles of ovulation and menstruation continued to be misunderstood by humans for hundreds of years. When did ovulation occur? Could women get pregnant while menstruating? What days were ideal for getting pregnant? No one had any clear answers.

It wasn’t until the 1920s that two gynecologists, Kyusaku Ogino in Japan and Hermann Knaus in Austria, committed themselves to untangling the mystery of ovulation; they concluded that it normally occurs 12 to 16 days before the start of a woman’s menstrual cycle, and that those were a woman’s “most fertile” days.  Shortly thereafter, Dr. Leo J. Latz built upon the Ogino-Knaus approach and published The Rhythm of Sterility and Fertility in Women, which instructed women to avoid sex for eight days (five days before ovulation, and three days after) to lower the risk of getting pregnant. “These findings of modern science disclose a rational, natural, and ethical means to space births and to regulate intelligently the number of children,” he wrote. Thus, the Rhythm Method was born.

But for many women, calculating the time of ovulation is tricky. No woman is the same, and many have irregular cycles—so one’s “fertile” days might change from month to month.  Fortunately, Dutch physician and gynecologist Theodoor Hendrik van de Velde gave women more confidence in using the Rhythm Method by using a thermometer. After charting female body temperature over a month, he discovered that a drop in basal body temperature coincided with ovulation:

“In general, he indicated, the course of the ideal temperature curve is as follows: Ovulation occurs when the curve is at its lowest point. With ovulation the curve rises fairly regularly to a more or less accentuated peak. At this point the ovum may be considered to be entirely disintegrated, and a new one about to burst forth from the Graafian follicle. The temperature now rapidly drops to the next low, when once more ovulation occurs” (454).

By simply wielding a thermometer and tracking the rhythm of their own basal body temperatures throughout the month, women across the world now had power over their reproductive abilities, without resorting to likely ineffective and potentially dangerous home methods of pregnancy prevention.  Even the Catholic Church, historically against any method of birth control, gave a stamp of approval for couples to use the Rhythm Method—in 1951, “Pope Pius XII sanctioned the rhythm method as a ‘natural’ method of regulating procreation.” In fact, a 1955 survey reported that over 65% of Catholic women said they used the Rhythm Method for family planning, and the method is still used today!

Hot Topic

The thermometer may not be the most glamourous or unusual method of birth control in history, but its impact on women across the world is undeniable. At a time when many women had little to no options for preventing pregnancy or regulating their own reproductive health, the thermometer and the creation of the Rhythm Method gave them a level of control over their own fertility. Even today, the Rhythm Method and “Basal Body Temperature” method are used by uterus-havers who prefer non-hormonal methods of birth control or hold religious or cultural beliefs that render other birth control methods unusable. 

If you’re interested in learning more about the history of the thermometer, the discovery of ovulation tracking, or simply want to explore the history of contraception as a whole, plan your next visit to the Dittrick Medical History Center at Case Western to see the Percy Skuy Collection and Gallery!  

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