Respecting the causes and origin of plague nothing is known. There cannot be the slightest doubt that it is propagated by absolute contact with, or a very near approach to, the bodies or clothes of persons infected ; but we are entirely at a loss to know how it is generated afresh. Ex tremes of temperature have a decided effect in putting a stop to it ; but Dr. Russell observed that, in the year 1761, the plague at Aleppo was mild, in 1762 it was severer, and in 1763 it was very fatal ; and yet there was no appreciable differ ence in the respective seasons of these years. In Egypt, the plague commences in autumn, and is regularly put an end to by the heats of summer ; and it is even asserted that contaminated goods are also disinfected at this time.
In Europe, the plague disappeared during the winter. This was remarked in all the epidemics, except that from 1636 to 1648, called the Great Plague, on account of its long duration ; but even in this instance it abated considerably during the winter. It was a common superstition that the plague abated on St. John's day.
The most fatal, and at the same time the most general epidemic, was that which ravaged Asia, Africa, and the whole of Europe, in the i4th cen tury. It was called by the northern European nations the Black Death,' and by the Italians 'la Mortilega Grande,' or the great mortality. Ac cording to Dr. Hecker, not less than twenty-five millions perished by it in the short space of three years, from 1347 to 135o. Since the commence. ment of this century, Europe has been free from the plague, with the exception of two or three in stances. It occurred at Noja, in the kingdom of Naples, in 1815 and ISI6 ; at the Lazaretto of Venice, inSi8 •' in Greiffenberg in Silesia in 18'9. It has not been seen in Great Britain since
the great epidemic of 1665, which is stated to have carried off eight thousand in one week. Quaran tine was first performed in one of the islands near Venice, in 1485. Persons who had been cured of plague in the Lazaretto on one of the adjoining islands were sent there, and all those with whom they had had intercourse, where they were detained forty days. This period was probably fixed upon on account of some medical hypothesis. The fortieth day was regarded as the last day of ardent diseases, and that which separated them from chronic. Forty days constituted the philosophical month of alchymists. Theological, and even legal derivations, have been also given. The forty days of the flood ; Moses' sojourn on Mount Sinai ; our Lord's fast ; and, lastly, what is called the ' Saxon term' (Sachsische Frist), which also lasts forty days. Bills of health were probably first established in 1507, by a council of health es tablished at Venice during a fatal plague that visited Italy for five years ; but they were not generally used until 1665. It is to these great measures that Europe is indebted for its present immunity from this terrible scourge ; and it cannot be doubted that, but for the callous indifference of the Orientals (which proceeds from their fatalism, love of gain, and ignorance), the same measures would be adopted in the East with the same suc cess. (Hecker's Hist. of the Epidemics of the Middle Ages; • Dr. Brown, art. ' Plague,' in Cydop. of Pract. Hed.; Dr. Russell, Hist. of Aleppo.)— W. A. N.