These are a few of the cases of direct inoculation which may be cited as of the simpler type. We shall next consider the rôle of the flea in the dissemination of the bubonic plague, an illustration complicated by the fact that the bacillus multiples within the insect and may be indirectly inoculated.
The Rôle of Fleas in the Transmission of the Plague
The plague is a specific infectious disease caused by Bacillus pestis. It occurs in several forms, of which the bubonic and the pneumonic are the most common. According to Wyman, 80 per cent of the human cases are of the bubonic type. It is a disease which, under the name of oriental plague, the pest, or the black death, has ravaged almost from time immemorial the countries of Africa, Asia, and Europe. The record of its ravages are almost beyond belief. In 542 A. D. it caused in one day ten thousand deaths in Constantinople. In the 14th century it was introduced from the East and prevailed throughout Armenia, Asia Minor, Egypt and Northern Africa and Europe. Hecker estimates that one-fourth of the population of Europe, or twenty-five million persons, died in the epidemic of that century. From then until the 17th century it was almost constantly present in Europe, the great plague of London, in 1665 killing 68,596 out of a population of 460,000. Such an epidemic would mean for New York City a proportionate loss of over 600,000 in a single year. It is little wonder that in the face of such an appalling disaster suspicion and credulity were rife and the wildest demoralization ensued.
During the 14th century the Jews were regarded as responsible for the disease, through poisoning wells, and were subjected to the most incredible persecution and torture. In Milan the visitation of 1630 was credited to the so-called anointers,—men who were supposed to spread the plague by anointing the walls with magic ointment—and the most horrible tortures that human ingenuity could devise were imposed on scores of victims, regardless of rank or of public service ([fig. 112, a]). Manzoni's great historical novel, "The Betrothed" has well pictured conditions in Italy during this period.
In modern times the plague is confined primarily to warm climates, a condition which has been brought about largely through general improvement in sanitary conditions.
At present, the hotbed of the disease is India, where there were 1,040,429 deaths in 1904 and where in a period of fifteen years, ending with January 1912, there were over 15,000,000 deaths. The reported deaths in that country for 1913 totaled 198,875.
During the winter of 1910-11 there occurred in Manchuria and North China a virulent epidemic of the pneumonic plague which caused the death of nearly 50,000 people. The question as to its origin and means of spread will be especially referred to later.