De tumoribus praeter naturam. In his Opera omnia, ed. cur. C.G. Kühn. 7, 705-32.

Galen’s classification of tumors persisted for more than 1,000 years. He considered neoplasms to be due to an excess of black bile, which solidified in certain sites. He advocated purges to dissolve the black bile, and if these were unsuccessful, the knife. He was not familiar with internal tumors. Critical edition and English translation by J. Reedy, Diss, (not published,) University of Michigan, 1968.