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PHYSIOLOGY: LOEB AND NORTHROP 
IS THERE A TEMPERATURE COEFFICIENT FOR THE 
DURATION OF LIFE? 
By Jacques Loeb and J. H. Northrop 
ROCKEFELLER INSTITUTE FOR MEDICAL RESEARCH. NEW YORK 
Received by the Academy, July 5, 1916 
In 1908 one of us raised the question whether there is a definite 
temperature coefficient for the duration of Hfe.^ This might be expected 
if the duration of life depended upon the presence of certain substances 
which were used up during Kfe; or if the duration of Hfe were hmited 
by the cumulative injurious effects of certain products of metabolism. 
Thus, Metchnikoff2 has mentioned the possibility that the duration of 
the life of the moth of the silk worin is limited by the retention of certain 
poisonous substances contained in the urine. The rapidity of con- 
sumption of the necessary substance in the case of the first or the velocity 
of the accumulation or action of injurious substances in the case of the 
second hypothesis should increase with the temperature according to a 
certain law. 
It seems that there exists for each species a pretty definite duration 
of life in spite of the fact that injuries of various types may shorten the 
life of the individual. The annual plants, the sequoia of the sierras, the 
human, the insects, have their characteristic duration of life. On the 
other hand, it was shown by Leo Loeb that the cancer cell is immortal 
and he pointed out that this might be the case for all cells. Then the 
problem arises, what is the cause of the fact that each species has a 
limited duration of life the magnitude of which is characteristic for the 
species? If the answer to this question is given by one of the two 
hypotheses mentioned in the first paragraph of this paper, it may be 
expected that there should be found a temperature coefficient for the 
duration of life of the order of magnitude of that of chemical reactions. 
A search for such a temperature coefficient can only be attempted on a 
form with a naturally short duration of life. We have selected for this 
purpose the fruit fly Drosophila. 
Newly hatched flies were put into large Erlenmeyer flasks kept in 
thermostats 34°, 31°, 28°, 24°, 14°, and 9°. Each flask contained on the 
average about 100 flies. The number of dead were counted each day 
and the surviving flies were put into fresh flasks every two days. Each 
determination of the duration of life was based upon at least two and 
often as many as twelve cultures of about 100 flies each. The values for 
the mean length of life of the flies in the separate cultures, at a given 
