This chapter reveals circuits of exchange among boards of health and European consuls serving in the Middle East that fashioned a European biopolity centered upon quarantine practice. It argues that, contrary to scholarship that has depicted quarantine prior to the 1850s as an improvised and irregular precursor to a late-century regime of international health, reciprocal correspondence among boards of health fostered a system that was durable and adaptable. The centerpiece of the chapter focuses on the events surrounding the passage of the 1825 Quarantine Act in Britain, in which an attempt to liberalize quarantine regulations led to a Continent-wide quarantine against British shipping. The spectacle only concluded when the Privy Council backed down. Rather than demonstrating British ambivalence, however, the reaction of the government in London shows how seriously politicians and advocates regarded membership in what one MP called the “family compact” of quarantine.