Otto Warburg, "On The Origin of Cancer Cells," SCIENCE, 
 (24FEB1956), Volume 123, Number 3191, pp. 309-314.

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 Professor Warburg is director of the Max Planck Institute for 
 Cell Physiology, Berlin-Dahlem, Germany.  This article is based 
 on a lecture delivered at Stuttgart on 25 May 1955 before the 
 German Central Committee for Cancer Control.  It was first 
 published in German [Naturwissenschaften 42, 401 (1955)].  This 
 translation was prepared by Dean Burk, Jehu Hunter, and W. H. 
 Everhardy of the U.S. Department of Health, Education, and 
 Welfare, Public Health Service, National Institutes of Health, 
 Bethesda, Md., with permission of Naturwissenschaften and with 
 collaboration of Professor Warburg, who has introduced 
 additional material.
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Abstract:

   Our principal experimental object for the measurement of the 
 metabolism of cancer cells is today no longer the tumor but the 
 ascites cancer cells (1) living free in the abdominal cavity, 
 which are almost pure cultures of cancer cells with which one 
 can work quantitatively as in chemical analysis.  Formerly, it 
 could be said of tumors, with their varying cancer cell content, 
 that they ferment more strongly the more cancer cells they 
 contain, but today we can determine the absolute fermentation 
 values of the cancer cells and find such high values that we 
 come very close to the fermentation values of wildly 
 proliferating Torula yeasts.

   What was formerly only qualitative has now become 
 quantitative. What was formerly only probably has now become 
 certain.  The era in which the fermentation of the cancer cells 
 or its importance could be disputed is over, and no one today 
 can doubt that we understand the origin of cancer cells if we 
 know how their large fermentation originates, or, to express it 
 more fully, if we know how the damaged respiration and the 
 excessive fermentation of the cancer cells originate.