The modern zoological garden developed in the nineteenth century as a site of instruction for the urban populace. In particular, the dual visions of bourgeois respectability and modern science shaped the institutional ethos of zoological gardens and, consequently, the spatial form of the site. Both visions dictated standards of decorum in exhibition design, the arrangement of exhibits, and the location of the zoo site in the city. The path of instruction from zoo directors to audience, however, was not unilateral. Rather, popular expectations of animal behaviour led zoo directors to broaden their standards of exhibition. One standard that remained throughout the nineteenth century was that the world was organized hierarchically between species, between humankind and animals, and between the contentious class structure of the industrial city.