Having thus, as briefly as the nature of the subject would allow, enumerated the several questions to which the doctrine of contagion has given rise, we now proceed to the consideration of those legislative enactments, by which different nations are enabled to ward off the calamities of Plague. It is generally admitted, that the plague has not originated in this country; and therefore, from its insular situation, the infection can only be introduced through the medium of ships. Egypt, the Levant, and other parts of the Mediterranean are seldom free from it, and hence it is chiefly through the medium of the commerce with these countries that the importation of the contagion is to be apprehended. To guard against this danger, the different governments require all ships sailing from any of these parts, to bring certificates from the magistracy of the port they last came from, declaring their country free from any contagious distemper: these are called “BILLS OF HEALTH,” and are distinguished as _clean_ or _foul_, as the place they come from may be healthy or infected. On the production of these bills it is determined by the Guardians of Health (in England, Custom-house officers) whether the vessel shall be permitted to trade or communicate, or, as it is technically expressed, be permitted to _pratique_ till she has performed a QUARANTINE[210] of as many days as the superintendants may in their judgment or caprice be pleased to direct. A period of _forty_ days (hence the term _Quarantine_) has been generally fixed upon as the maximum of this seclusion, on the expiration of which it is customary abroad for physicians, accompanied by some members of the board of health, who are frequently merchants of the place, to examine the ship’s crew; and strict search is made on board, by persons appointed to see whether the number of sailors and passengers corresponds with those mentioned in the bills of health, and if any difference appears it will be difficult in any country to obtain admission to _pratique_, or at least it will be necessary to perform a full quarantine from the time of such detection.