As this is a world of innumerable lives, it will always show innumerable lives; each life having its power, constructive or destructive, will show that power even in a microbe; and so this discovery of microbes of diseases will go on with the increase of diseases, for to prevent microbes from existing is not always in the power of man. Sometimes he will destroy them, but often he will find that each microbe destroyed will produce in return many more microbes. What is life? Every atom of it is living, call it ray or electron, germ or microbe.