This collection includes the original cancer research papers by Dr. Otto Warburg and his colleagues in their original text. It includes additional articles NOT found in “The Metabolism of Tumours.”

The collection includes these articles:

—The Prime Cause and Prevention of Cancer

—On the Origin of Cancer Cells

—The Metabolism of Tumours in the Body

—On the Respiratory Impairment of Cancer Cells

—The Chemical Constitution of Respiration Ferment

—The Oxygen Transferring Ferment of Respiration

—The Metabolism of Carcinoma Cells

—The Carbohydrate Metabolism of Tumours

—Observation on the Carbohydrate Metabolism of Tumours

—Enzymic Studies on Ascitic Tumours and Their Host’s Blood Plasmas

If a lowered oxygen pressure during cell growth may cause cancer, or, more generally, if any inhibition of respiration during growth may cause cancer, then a next problem is to show why reduced respiration induces cancer. Since we already know that with a lowering of respiration fermentation results, we can re- express our question: Why does cancer result if oxygen-respiration is replaced by fermentation? 

The early history of life on our planet indicates that life existed on earth before the earth’s atmosphere contained free oxygen gas. The living cells must therefore have been fermenting cells then, and, as fossils show, they were undifferentiated single cells. Only when free oxygen appeared in the atmosphere - some billion years ago - did the higher development of life set in, to produce the plant and animal kingdoms from the fermenting, undifferentiated single cells. What the philosophers of life have called "Evolution créatrice" has been and is therefore the work of oxygen. 

The reverse process, the dedifferentiation of life, takes place today in greatest amount before our eyes in cancer development, which is another expression for dedifferentiation. To be sure, cancer development takes place even in the presence of free oxygen gas in the atmosphere, but this oxygen may not penetrate in sufficient quantity into the growing body cells, or the respiratory apo-enzymes of the growing body cells may not be saturated with the active groups. In any case, during the cancer development the oxygen-respiration always falls, fermentation appears, and the highly differentiated cells are transformed to fermenting anaerobes, which have lost all their body functions and retain only the now useless property of growth. Thus, when respiration disappears, life does not disappear, but the meaning of life disappears, and what remains are growing machines that destroy the body in which they grow.