Historical medical theories encompass a range of ideas about health and disease that have evolved over time. In ancient civilizations, such as those in Greece and Egypt, people believed that illnesses were caused by imbalances in bodily fluids, known as the humoral theory. This theory suggested that maintaining balance among the four humors—blood, phlegm, black bile, and yellow bile—was essential for good health. During the Middle Ages, the influence of Galileo and Hippocrates led to the development of more systematic approaches to medicine. The Germ Theory emerged in the 19th century, proposing that microorganisms cause diseases, fundamentally changing medical practices and leading to advancements in hygiene and treatment. These historical theories laid the groundwork for modern medicine.