Greek doctor Hippocrates created the Theory of the Four Humours stating the body was made of 4 substances (humours) - blood, phlegm, yellowbile and black bile. They were linked to the seasons and 4 elements. Disease was caused if the humours were 'unbalanced'.
Greek doctor Galen developed Hippocrates' ideas and believed in the Theory of Opposites. To treat someone with unbalanced humours, they would be given food, drink, herbs or spices to balance the humours.
Hippocrates' and Galen's ideas were taught for centuries so weren't challenged so limited progress was made in medicine.
The RomanCatholic Church supported Hippocrates and Galen and texts approved by the Church were difficult to challenge.
Galen only dissected animals so his ideas about human anatomy were wrong impeding doctors.
