<span>It's a metaphor, darling. A nursery (whether it's a plant nursery or a nursery school) is a place where small plants or human beings are carefully nutured so that they can grow. "He" (whoever this mysterious "he" is that you're referring to) is asserting that factories are places where bad things like "disease and vice" can similarly grow and flourish.</span>
They were fast moving so they took over lots of land then united them by faith. It also helped that they controlled the Silk Road, the biggest trade network between Europe and Asia.
