ABSTRACT
The word cancer originates from the writings of Hippocrates, who observed distended vessels radiating from a central lump in the breast like the legs of a crab. Galen believed that cancer was the result of an excess of black bile, the same humour responsible for the state of melancholy (this word literally means black bile). The nature of blood, yellow bile and phlegm is now widely understood, but black bile is a much more mysterious substance. In the sixteenth and seventeenth centuries, chemical ideas were being applied to the practice of medicine. The demise of the humoral and chemical theories came in the eighteenth and nineteenth centuries when the structure of the body was conceived as a set of different tissues. Theories on the cause of cancer have ranged from external agents in the form of infectious organisms, environmental chemicals and physical factors (notably radiation), to constitutional factors such as genetic mutations.
