Society can be thought of as a living body which is a collection of individual 'cells' acting cooperatively. The human lymphoid mechanisms have been described as a kind of police system in the body, and if they fail, cancer can develop. Like cancer cells, society continually produces to prevent law-abiders from contracting criminality, which may be described as infectious and is an environmental hazard. The environment consists of people and their intentions, energy flows and sustenance, and space and planning. In terms of people's intentions, the fear of crime is probably the most important aspect of the man-made social environment because it affects so many other facets of social living. The police can affect the fear of crime through public information and appropriate strategies. Energy and power are important issues, because the power of the police must be energetically directed to benefit law-abiders. It appears that the criminal population is increasing, and the predator-prey analogy may help to determine police resource allocation. An animal ecologist might recommend culling an overpopulated predator group. A plant ecologist might recommend genetically improving plant stock or integrating an associate plant to provide protection from pests and contagious weeds. Human ecologists might recommend suitable methods for containment of criminals and strengthening law-abiders. An ecological approach is commensurate with the police function of helping to maintain society. Seventy-four references are provided.