COLD LIGHT? 
’ By E. Newron Harvey, Pu. D. 
Professor of Physiology, Princeton University 
Man may well pride himself upon the development of heat, light, 
and electricity. Modern comfort is dependent on them. Few would 
welcome their disappearance despite the present tendency to decry 
the complexity of a mechanical age. But let us not forget that living 
creatures have long possessed methods of producing heat, light, 
and electricity quite different from those of the furnace, the lamp, or 
the dynamo. 
Mammals and birds maintain their body temperature continually 
above that of their surroundings. They possess eternal fires and effi- 
cient thermoregulation, which makes them independent of cold. 
Fireflies and other luminous animals have flashed their lights for 
countless ages, while electric fish can generate currents strong enough 
to ring a bell or light an incandescent lamp. 
We speak of the production of light by living things as biolumi- 
nescence, and few subjects touch as diverse fields of inquiry or interest 
as many investigators. It appeals to the morphologist, the physi- 
ologist, the chemist, the physicist, the philosopher, and the illuminat- 
ing engineer. Those who have seen the brilliant flashes of innumer- 
able fireflies, filling the fields on a midsummer night, or the sea a 
vivid sheet of flame when disturbed by some passing ship, can not 
but marvel at the display. Slow is the imagination which will not 
inquire how and why this light is emitted, or whether we may not 
some day successfully develop a “cold light,” modeled on nature’s 
plan. 
It is possible in the space at my disposal to state only the general 
facts of bioluminescence and discuss some recent experiments bearing 
on the physical chemistry of the process. While fireflies have been 
known for centuries to all people, it is about 50 years since we 
have recognized the cause of certain other phosphorescences of liv- 
ing things. The glowing of dead fish or the glowing of meat in 
refrigerators. or the glowing of wood were definitely proved to be 
due to living organisms in 1875 when it was shown that these lumi- 
nescences were of plant or animal origin. 
1 Reprinted by permission from Princeton Alumni Weekly, Vol. XXVI, No. 33, June 2, 
1926. Appeared also in Scientia, May, 1927. 
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