66:5.20
The great obstacle in the way of promoting hygiene among these ignorant peoples consisted in the fact that the real causes of many diseases were too small to be seen by the naked eye, and also because they all held fire in superstitious regard. It required thousands of years to persuade them to burn refuse. In the meantime they were urged to bury their decaying rubbish. The great sanitary advance of this epoch came from the dissemination of knowledge regarding the health-giving and disease-destroying properties of sunlight.