If the great practical truth, taught by modern investigation and experience, be, that the only real security against any kind and degree of epidemic disease is an abundant and constant supply of pure air, the prevention of overcrowding, and the dispersion of the sick; and if, as is generally agreed, confinement in a foul atmosphere can convert common fever into pestilence, and ventilation and dispersion can dissipate any contagion, then quarantine must be not only useless but pernicious, since the invariable effect of quarantine as hitherto practised in all countries has been the congregation and confinement of the sick, and of those who, though not actually sick, are suspected to have in them the seeds of disease, requiring only a few days or hours for their development,—the congregation and confinement of such persons in a limited space, often in a filthy ship and an unhealthy locality, and always under circumstances calculated to excite apprehension and alarm—conditions in the highest degree favourable to the generation and spread of disease: it follows that quarantine, instead of guarding against and preventing disease, fosters and concentrates it, and places it under conditions the most favourable that can be devised for its general extension; and therefore must not only fail to accomplish its object, but tend to produce the very calamity which it endeavours to prevent. * * * * * The principal ground on which objection is made to the continuance of quarantine is that the fundamental principle on which it is based is fallacious, and that the only means of preventing the origin and spread of epidemic disease is the adoption of sanitary measures. Substitution of sanitary measures for quarantine restrictions would render the importation of any disease from one country into another in the highest degree improbable.