Quotes from Charles V. Chapin, M.D.

Since the development of bacteriology, many have been inclined to forget that, as it takes two to make a quarrel, so it takes two to make a disease, the microbe and its host. There is a constant struggle between disease germs and the bodies of animals and of human beings that they invade. There is also a tendency for an equilibrium to become established. The germs kill off the most susceptible and immunize the more resistant.