Notwithstanding the many measures that have been directed against plague infection in seaports, its presence continues, so that it is not uncommon to hear the belief expressed that "wherever the disease gains a firm foothold it can not be eradicated." Is it not possible that we have been doing too much in some directions and too little in others? Strict maritime quarantine, general house cleaning and whitewashing, poisoning and trapping of rats, immunization with Haffkine's serum of persons likely to be exposed, isolation of contacts, forbidding of overcrowding, burning of infected districts, etc., have been enforced as well as possible.
It is generally admitted that the principal carriers of infection are the rats and their fleas, but unquestionably there are other carriers, particularly insects. A campaign directed against the principal carriers, when restricted to poisoning and trapping, can accomplish but temporary good. Rats are killed for the reason that "without