The study of constitutional law often begins with a dispute between two different versions of the relationship of the individual to the state. There are those who think that atomistic individuals come together by a set of voluntary contracts, and those who think that societies should be treated as though they are complex organisms that cannot be understood simply as the sum of their parts. In general, I think that these organic arguments can lead to heavily collective institutions whose operations and ambitions I discuss. However, in this case I want to examine the problem of the constitution as though it were a study in social biology. I hope therefore to draw out comparisons of the organisation of the human body on the one hand with those of the state on the other. There are always dangers in making this transition, but the insights that are garnered should be useful enough to make the risk worth bearing. I begin with an account of the distribution of functions in the human body in order to provide a template for understanding the organisation of other types of system. From there, it is a simple progression to consider the workings of a family, a business and, finally, a state.