Before the discovery of chemical elements or particle physics, it was believed everything was made of the elements of fire, water, air, ether and earth in different proportions and combinations. This idea came from Ancient Greek philosophy and was common until the late eighteenth century.
In the same period, the health and function of the body was believed to be governed by the four humours: black bile, yellow bile, phlegm and blood. Imbalances of humours led to sickness and different types of disposition. This theory was first put forward by Hippocrates and was widely believed (even by doctors) until the nineteenth century.