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HISTORY  |
The ancient Egyptians moved their hands across the surface of the body to scan and monitor changes in temperature. The fingers acted as sensors and the brain interpreted the relevant changes. They could effectively evaluate the rise in temperature over a period of time. It could be isolated to a specific area, or determined that there was a general increase over the entire body. The Greek Physician, Hippocrates, wrote in 400 B.C. "In whatever part of the body excess of heat or cold is felt, the disease is there to be discovered." The ancient Greeks immersed the body in wet mud. The area that dried more quickly indicated a warmer region, and was considered the diseased tissue. (ref. Thermography & Personal Injury Litigation. Wiley Law Publications, Samuel Hodge Jr., 1987. pg. 71) |
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Heat is a property of the body.
Temperature refers to a certain standard of reference. The
use of hands to measure heat emanating from the body
remained well into the sixteenth and seventeenth
centuries. It wasn't until Galileo, who made a thermoscope
from a glass tube, that some form of temperature sensing
device was developed, but it did not have a scale. It was the work of Fahrenheit, who fixed a lower point by using salt with ice water and ranged to boiling water at 212 degrees. Celsius, in 1742, created a decimal scale, using "zero" as the boiling point of water and 100 as the freezing point. His scale was reversed by the Swedish botanist Linnaeus. Increasing heat was indicated by higher temperatures. Prof. Carl Wunderlich of Leipzig in 1868 advanced the use of thermometry in medicine with the first set of temperature charts on individual patients with a wide range of diseases. He proposed the design of the present day clinical thermometer, which is now slowly being replaced by disposable sterile thermocouples and radiometers for middle ear temperature. (ref. Prof. E.F.J. Ring, Royal National Hospital for Rheumatic Diseases, Bath, England. University of Glamorgan - Inaugural Lecture Jan. 28th, 1997) |
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use of liquid crystals became another method of displaying
skin temperature. Cholesteric esters can have the property
of changing color with temperature, and this was
established by Lehmann in 1877. The practical application
involved the use of elaborate panels that encapsulated the
crystals and were applied to the surface of the skin, but
due to a large area of contact, they affected the
temperature of the skin.
All the above methods for
measuring human body temperature are contact methods.
The major advances of the last 30 years have been with
infrared thermal imaging.The surface of the human body
is a highly efficient radiator and it is possible to
detect the infrared emission from the skin, and create a
thermal map of temperature distribution by remote
sensing. (ref. Prof. E.F.J. Ring,
Royal National Hospital for Rheumatic Diseases, Bath,
England. University of Glamorgan - Inaugural Lecture
Jan. 28th, 1997) The astronomer, Sir
William Herschel, in Bath, England, discovered the
existence of infrared radiation by trying to measure the
heat of the separate colors of the rainbow spectrum cast
on a table in a darkened room. He found the highest
temperature to fall beyond the red end, which he
reported to the Royal Society as Dark Heat in 1800. His
son, Sir John Herschel, who was more interested in
photography, managed to record the heating rays on the
infra red side of red by creating an evaporograph image
using carbon suspension in alcohol. He termed this image
a thermogram. The foundation was laid for the advances
that would come over a century later with the
sophisticated thermal imaging devices that are used in
military, industrial and medical applications. |
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