How did Herbert Spencer compare human societies with biological organisms?

Herbert Spencer drew a detailed analogy between biological organisms and human societies, viewing both as systems that evolve toward increasing complexity through the division of labour.1

He mapped specific biological functions to social structures:
* Regulative system: The central nervous system in animals corresponds to government in society.1
* Sustaining system: Alimentation in animals corresponds to industry in society.1
* Distribution system: Veins and arteries in animals correspond to roads, telegraphs, and similar infrastructure in society.1

Despite these parallels, Spencer emphasized a fundamental distinction: in an animal, the various parts exist for the benefit of the whole organism, which possesses a single consciousness. In contrast, he argued that society exists for the benefit of its individual members, each of whom retains their own consciousness. This commitment to individualism was central to his work, as he believed society should not be treated as an entity superior to the individuals who compose it.12