Doctor's Review: Medicine on the Move

October 28, 2021
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Believe it or not, the simple thermometer was centuries in the making

With the warm weather finally here, most winter-weary Canadian physicians are looking forward to some much-deserved time off. But as the summer season heats up, few doctors (if any) will give much thought to how the mercury actually rises... so long as it does! Climatological chit-chat aside, we all know that gauging the temperature of the human body is an essential diagnostic tool -- one medical practitioners have been able to take for granted for nearly a century and a half. Indeed, where would we be without the simple thermometer, one of the easiest ways to detect infection and/or physical distress?

Of course, there are good old-fashioned ways of knowing whether someone's running a fever; often you can tell with a simple glance, whether that someone's your child or your patient. But placing your wrist on a forehead is simply not as reliable as a thermometer and not nearly as accurate. Historically speaking, the first step in figuring out what was going on inside was figuring out what was happening outside, and so the innovation was born not as a medical marvel, but rather as a tool of the first weather watchers.


The legendary Italian mathematician, physicist and astronomer Galileo (1564-1642) was the first to devise an instrument to determine the exterior temperature. The Galilean thermoscope, as it was called, made its debut in 1593 -- a sealed glass tube containing water, suspended within which were several other, smaller glass balls, each also containing liquid (usually alcohol). As the room temperature changed, the various balls would rise and fall. Galileo's next version was an air thermoscope. This he accomplished by heating a glass tube and then immersing its one open end into water; as the tube cooled to room temperature, the decreasing air pressure within would cause water to be sucked up through the shaft. Afterwards, any subsequent temperature shifts would result in changes to the water level. A great idea to be sure, but both devices could only track changes in temperature, not reveal the temperature itself. The thermoscopes were crude, adversely affected by atmospheric pressure and not particularly accurate, but they were a start.

Another Italian, the physiologist, inventor and amateur climatologist Sanctorius of Padua (1561-1636), improved on Galileo's air thermoscope by adding a scale in 1612, which made it far more useful, though no more accurate. He did, however, become the first to use a thermoscope of sorts to measure the temperature of the human body. It had been known since the time of Hippocrates and Galen that when sick, the human body sometimes responds by a rise in temperature. Sanctorius wanted to quantify this temperature change and invented a special air thermoscope to this end. It was huge and took forever, but it was a medical milestone nevertheless. Perhaps as a foil to all these hot bodies, Sanctorius thoughtfully invented one of the earliest waterbeds as well.

Taking a patient's temperature accurately and relatively effectively would require a few more years yet. Paving the way for better temperature-taking was an unlikely hero: Duke Ferdinand II of Tuscany (1610-1670). Though the nobleman -- a much-loved leader and patron of the sciences, like many of his de Medici relatives -- could have sat around all day on his duff eating bonbons, he preferred tinkering about with medical gadgets instead. In the mid 1600s, the Duke discovered that a completely sealed liquid-in-glass thermoscope worked far better than the open-ended variety pioneered by his predecessors, instruments whose susceptibility to changes in barometric pressure caused them to be unreliable.

The Duke also preferred to use alcohol instead of water in his instruments, but overall this made little difference. Though more useful than earlier versions, these thermoscopes had limited applicability in the real world. They were large and quite delicate -- a problem that soon became apparent when they were brought to sea, where the rolling motion of the ships rendered them nearly useless. And then there was still the issue of no standardized scale.


Enter Daniel Gabriel Fahrenheit (1686-1736), the well-known German physicist with a convenient knack for numbers. Fahrenheit was interested in science, but after both his parents died in a tragic poison-mushroom-eating incident, he was forced to take up a trade glassblowing. Fahrenheit combined his love of glass and his love of science by inventing new and improved versions of scientific instruments such as altimeters, barometers and thermometers. His natural talents in physics and chemistry earned him a great deal of respect, and he was even admitted to the Royal Society in 1724.

Fahrenheit's first thermometer (1709) used alcohol, but he found the liquid to be too temperamental. To solve the problem, Fahrenheit built on the work of the notable deaf physicist Guillaume Amontons (1663-1705), who was the first to use the far thicker liquid mercury in a thermometer. As for the issue of standardizing temperature readings, he simply created his own scale. Plus, by using thinly blown glass tubes, he was also able to add more points to his scale, allowing for far greater accuracy (though the device was still long and unwieldy).

In 1714, Fahrenheit debuted his new-and-improved closed-glass mercury thermometer along with the first version of his very own eponymously named temperature thrown in for good measure. After a few adjustments, he eventually settled on the following set points: the lowest known recorded temperature at the time as 0°, the freezing point of water at 32°, and the boiling point of water at 212°. Later on, a couple of scientists named Celsius (1742) and Kelvin (1848) would come along and usurp Fahrenheit with better scales of their own, but Herr Fahrenheit was the one who started it all when he stated the normal human body temperature to be 90° (later adjusted to 96 and then 98.6). His was the first scale to be used ubiquitously and internationally.


Last year marked the 140th anniversary of the first time a short thermometer was used for medical use to determine the temperature of the human body, a milestone for which we have English physician Sir Thomas Clifford Allbutt to thank. He was born on July 20th, 1836, in the town of Dewsbury in Yorkshire. Though he enjoyed history, art, writing and the classics, young Thomas had a keen scientific mind and settled on medicine as his field of choice. After completing his training at St. Peter's School in Cambridge and St. George's Hospital, he opened shop as a general physician in Leeds, where he would enjoy a thriving practice and excellent professional reputation for nearly 30 years.

The doctor also enjoyed tinkering about with his hands, and was among those who pioneered the routine use of the ophthalmoscope during medical examinations. But perhaps his most important contribution to medicine was the creation of the first clinical thermometer in 1866. After much trial and error, he refined the instrument from a foot-long hand-held behemoth that required at least 20 minutes to provide an accurate temperature reading, to a short and quick diagnostic tool that remained virtually unchanged for nearly a century and a half.

The beloved Dr Allbutt was named the regius professor of physic at Cambridge University in 1892. (It was during his years there that he even befriended his counterpart at Oxford -- Sir William Osler!) In recognition of his many contributions to the field of medicine -- which also included notable ameliorations in the treatment of various arterial diseases, and undertaking the writing and editing of the vast, multi-volume Systems of Medicine, the encyclopedic go-to medical tome at the time -- he was knighted in 1907. Dr Allbutt died on February 22, 1925, in Cambridge.


Since Dr Allbutt's innovations, various refinements have been made to the thermometer. Aside from the modern electronic versions, some of the biggest changes in temperature-taking came when the ear thermometer was invented by a German surgeon named Theodore Hannes Benzinger during World War II, followed by the introduction of the infrared thermometer in 1984. Despite the dubious accuracy of the ear thermometer, countless mothers daunted by the old-fashioned way of taking their infants' temperature applauded its ease of use.

Other recent improvements in the medical and industrial thermometers include the now-standard digital thermometer, phase-change (or dot-matrix) and liquid-crystal versions, as well as the so-called temporal scanner, applied to the temporal artery. For people around the world, however, none replace the ease of use and accuracy afforded by the short clinical thermometer invented by Allbutt, though the mercury has been replaced in recent years with different, safer substances. In the last few years, the American Academy of Pediatrics, the US Environmental Protection Agency and Environment Canada have all begun recommending the elimination of mercury thermometers in the home. Although the chances of mercury poisoning from broken thermometers are slim, safer and equally effective alternatives exist.

Oh, and lest the elephant in the room go unnoticed, it is unfortunately not known whether or not the aptly named inventor of the short clinical thermometer was himself ever teased about his surname…


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