Émile Durkheim, drawing on the analogies between biological and social systems popularized by Herbert Spencer and others, introduced the idea that diverse social institutions and practices played a role in assuring the functional integration of society through assimilation of diverse parts into a unified and self-reproducing whole. In this context, Durkheim distinguished two forms of structural relationship: mechanical solidarity and organic solidarity. The former describes structures that unite similar parts through a shared culture, while the latter describes differentiated parts united through social exchange and material interdependence.