In 1960, Dr. Ban R. Potter and Dr. Henry Pitot (at McCardle Laboratory in Madison, Wisconsin), Dr. Tetsuo Ono (then at McCardle Laboratory and now at the Japanese Foundation for Cancer Research in Tokyo, Japan) and Dr. Harold P. Morris (then at the National Cancer Institute and now at Howard University, Washington, D.C.) decided that an experimental cancer model would be an invaluable tool to examine neoplastic changes in cells. Since they were studying the various highly specific metabolic processes which are unique to liver tissues, they determined that a transplantable liver cancer model would be the ideal system to work with. This system would provide for comparison of normal liver tissue of the non-tumor bearing animal, the tumor bearing animal's (host) liver and the liver cancer. Dr. Morris undertook a series of rat studies employing several chemicals known to cause liver cancer. Soon the first Morris hepatomas (#3683, 3924A, 5123) were being studied by several labs. During the next 18 years, Dr. Morris developed and transplanted numerous strains of hepatomas of which no two were identical. These tumors ranged from the very slowly-growing, highly differentiated cancer tissues, e.g., 9618A which is a diploid tumor containing glycogen and a "nearly normal" complement of enzymes, to a large group of rapidly-growing, poorly differentiated cancer tissues, e.g., 3924A and 9618A2 (latter being derived from 9618A) both of which are heteroploid and have lost almost all of their complement of enzymes which carry out the differentiated functions of liver tissue. This spectrum of cancer tissues has been and is now being utilized by hundreds of laboratories located all over the world. It has provided cancer researchers with a stable population of cancer cells for examining every parameter of molecular and cellular functioning. The spectrum of Morris hepatoma has provided us up to now with the most complete understanding possible of cancer tissues in action. We now know more about the "typical" cancer tissue, from the hundreds of reports on the Morris hepatomas, than from any other single cancer model system. The present book represents the first attempt to accumulate and review our knowledge about cancer as gained during the last two decades from studying the Morris hepatomas. It provides the reader with a beautiful example of the open sharing of scientific ideas and concepts and it elegantly demonstrates how the devoted cooperation among scientists can truly yield highly synergistic results. It gives a clearer picture of the origin, evolution, and demise of cancer theories. And it also provides the reader with a distinct preview of new cancer theories which may now be present on the horizon.