The connection between body heat or fever and disease was
made millennia ago, but the clinical utility of body temperature was not fully
understood until the 1800s.
Although it would be many years later that physicians would finally
understand that a raised body temperature meant increased antibody production
in the face of disease, early experiments with temperature readings helped the
profession to begin to track the progression of diseases, even if doctors could
do little to treat them.
Many centuries ago, instead of indicating underlying disease of
infection, fever was thought to be the disease itself. If you had one, it was
patent for a clinical thermometer, which was designed to be able to
be heated to a point higher than marked on its temperature scale without
breaking. This would allow the instrument to be heated to a boiling point for
purposes of sterilization.
Source: United States Patent and
Trademark Office; Google Patent Search
Fever was detected by laying the hand on the patients flesh.
Inflamed parts of the body were hot to the touch, often indicating infection.
This was recognized as early as Hippocrates, who insisted that physicians
examine temperature, recognize its signs and use agents to elevate the
temperature when depressed and lower it when raised. This, combined with
an accelerated pulse, was used as an indicator of the success of many early
medical treatments, such as bloodletting. When blood was let, the patient
cooled and their pulse slowed, indicating to the physician that the fever was
However, with the early invention of an open thermometer by Galileo in
the late 1500s, efforts began to adapt the invention for use to measure the
temperature of the human body.
About the year 1612, Sanctorio Sanctorius invented the first crude
version of a thermometer as we think of it today. He described the invention in
De Statica Medicina in 1614. Sanctorio was probably the first
physician to try to begin to draw conclusions about disease based on
thermometer readings. His early versions of the instrument were unwieldy and
often required a long time to get an accurate reading.
A breakthrough came in 1714 when Gabriel Fahrenheit invented the mercury
thermometer. Mercury, he found, expanded and contracted more rapidly than
water, allowing physicians to obtain a patients temperature faster.
The instrument began to gain popularity in medicine with the help of
Hermann Boerhaave, or more specifically, his two students Gerard L.B. Van
Swieten, founder of the Viennese School of Medicine, and Anton De Haen. De Haen
was an instructor at the Vienna Hospital and he integrated the use of the
thermometer into his bedside routine. He instructed his students that the
thermometer was a much more accurate way to determine fever than the hand and
made several observations about thermometry. These included the increase in
temperature in the elderly, the difference in perceived temperature of a
patient and actual temperature, and the change in temperature as a sign of
Several decades later, Antoine Cesar Becquerel and Gilbert Breschet were
the first to determine that 37ºC or 98.6ºF was the body temperature
of a healthy adult.
However, the early definitive work on the clinical utility of body
temperature was published by Carl Wunderlich in 1868. Das Verhalten der
Eigenwarme in Krankheiten was the culmination of 15 years of observation
of temperatures in hospital wards. Starting in about 1851, Wunderlich began to
take patients' temperatures at least twice a day, up to as many as four to six
times a day, when a patient had a fever. With this data, taken from
approximately 25,000 patients, he was able to define and chart certain traits
that tracked the progression of diseases proving that disease obeyed
As the popularity of thermometry grew among physicians, a desire also
grew to adapt the practice to be more useful to everyday doctoring. At the
time, the most popular place for determining temperature was a patients
armpit. Other areas, such as the groin, rectum, urethra or vagina where
considered too intimate and the mouth too germ-riddled. It was not until the
end of the 1800s and the recognition of the importance of alcohol and other
agents as disinfectants that oral thermometry grew in popularity.
The design of the thermometer, from an often foot-long model that took
20 minutes to get a reading to a more portable six-inch model that took five
minutes to get a reading, is credited to Thomas Clifford Allbutt in 1866.
The evolution of clinical thermometry in the United States is credited
to Edouard Seguin and his son, Edward. In 1866, the junior Seguin and William
H. Draper began to use the practice regularly in New York Hospital. Using
thermometry Seguin first coined the term vital signs for
temperature, pulse and respiration. He and Draper charted the progress of
fevers together with patient vital signs and distinguished symptoms and signs
of diseases such as typhus, typhoid and others. Draper tracked these
observations in a chart, which he attached to hospital beds, a trend that would
spread to most hospitals in the country within a few decades.
By 1870, Seguin was promoting the use of thermometry in homes as well as
hospitals. The instrument was described as a tool for mothers to provide useful
information to physicians and to escape the clutches of medical quackery.
However, despite physicians ever-increasing knowledge of fever,
medicine provided few remedies for it. It was not until 1975 that it was
understood by the medical community that fever served a function. The increase
in body temperature associated with a fever resulted in an increase in antibody
production, which helped to fight infection. In fact, in 1993 the World Health
Organization recommended against the use of drugs that reduce fevers in
children in developing countries. But this recommendation may be harder to
accept in developed countries where medicines are much more readily available
and the comfort of the patient is often a high priority.
Since its invention, the thermometer has changed and adapted as science
and technology advanced. Although the appearance may have changed, the basic
function of the instrument has not. by Leah Lawrence
For more information:
- Blumenthal I. J R Soc Med. 1997;90:391-394.
- Haller JS. West J Med. 1985;142:108-116.
- Pearce JMS. Q J Med. 2002;95:251-252.