For a short period the plague seemed to have disappeared altogether. Those who cherished this hope were, however, destined to disappointment. In 1853 an outbreak occurred in the Assyr country, Western Arabia; and from that time till the present unmistakable local epidemics of the bubo plague have occurred in isolated regions of Africa and Asia; thus, in 1858 at Benghazi in Tripoli; in 1857 in Mesopotamia; in 1863 in the district of Maku, Persian Kurdistan; in 1867 in the marsh district on the right bank of the Euphrates; in 1870 in Persian Kurdistan; in 1871-73 in the Yunnan province, Western China; in 1873 in the marsh district on the left bank of the Euphrates. During four years following the outbreak of 1873 the disease continued to prevail over an extensive area in the countries bordering on the northern banks of the Persian Gulf. In 1874 it reappeared also in the Assyr district, Western Arabia, and in Benghazi, Northern Africa. In 1876, whilst still infesting the regions about the Lower Euphrates, the plague appeared in South-eastern Persia, and during this and the following years it appeared at several isolated points on the borders of the Caspian Sea. Early in 1878 the disease was reported as prevailing in the district of Souj-Bulak, Persian Kurdistan, and it appeared in October of the same year at the Cossack village Vetlanka, on the Lower Volga, district of Astrakhan, Russia, after an absence from Europe of thirty-seven years. It has more recently prevailed in the Assyr district, Western Arabia, and there have been rumors of its reappearances in Persian Kurdistan.
The Indian or Pali plague (Máhámari) has prevailed in local epidemics of great severity on several occasions during the present century in the North-western provinces of India. This fever was first recognized in Kutch in May, 1815, after a season of great scarcity of food. It spread rapidly over an extensive territory, and appeared in the spring of the following year at various points in Guzerat, next in Merawi, later in Rhadenpur, spreading thence westward to Sindh. Not until the following year (1817) did the pest reach the British possessions. This epidemic continued to prevail until 1821. The disease did not reappear until July 6, 1836, when it broke out in Pali, the principal dépôt of traffic between the coast and North-western India. It spread with great rapidity to the adjoining provinces. Toward the close of the year 1837 the disease broke out anew in Pali, and raged until the spring of the following year. In 1834-35, again in 1837, there were outbreaks of this pest in Gurwal, and in 1846 and 1847 in Karmoun, provinces of the southern slopes of the Himalayas. This destructive pest has raged at an altitude of 10,300 feet, and we learn from Hirsch that it has never wholly disappeared from the mountain-districts of the Himalayas since 1823, and that its ravages in these regions have been so great that certain settlements have been wholly destroyed.
The fever was remittent in type, with a great tendency to become continued; it was characterized by rapidly developing extreme prostration, and was very fatal. In most cases there were glandular swellings in the groins, armpits, and neck. Carbuncles and petechiæ are not mentioned as having been observed. Dyspnoea, cough, and bloody expectoration were frequent symptoms. Vomiting, at first of bilious matter, later of dark, coffee-colored fluid, was likewise common.
The plague has never appeared in the western hemisphere.
ETIOLOGY.—1. Predisposing Influences.—Whilst the present views as to the causation of the specific diseases compel us to assume a specific infecting principle as the real cause of every outbreak of the plague, there are certain circumstances which are recognized as so favoring the development and action of that principle that they have come to be looked upon as indirect or auxiliary causes of particular epidemics. It is more in accordance with the facts to speak of them as predisposing influences. Chief among these circumstances is that combination of physical and social wretchedness which goes hand in hand with poverty and overcrowding. The plague has been termed by a recent observer (Cabiadis) miseriæ morbus, and he has thus reproduced in 1878 a name applied to the great plague of London in 1665—the poor's plague. All observers of recent epidemics unite in ascribing to poverty the foremost rank among the predisposing influences of plague epidemics. It is only necessary to enumerate the evils which form the train of poverty, whether in cities or in villages, to complete the list.
With poverty come ignorance and neglect of all sanitary laws; overcrowding and ill ventilation; personal filthiness; improper as well as insufficient diet; indifference as to the location of dwellings and their surroundings. The condition of the villages which have been the scene of some of the recent epidemics beggars description. All observers unite in testifying to such accumulations of filth in and around the houses as requires to be seen to be believed. In these communities latrines are unknown, and no such thing as organized scavenging has ever existed.
The accumulation of unburied or imperfectly buried corpses has been looked upon as the real cause of the plague, and some of the recent epidemics have followed the prevalence of distinctive epizoötics. Whilst it is not difficult to disprove that under ordinary circumstances the effluvia from exposed and rotting carcasses can give rise to outbreaks of the plague, it is more than probable that an atmosphere charged with such emanations (together with other causes) can so unfavorably influence a community as to increase its susceptibility to the specific cause of this or any other infective disease. There can be but little doubt that the dead bodies of the victims of the plague are capable of disseminating the disease, and that the reopening of graves containing such bodies, even after a long period of time, has given rise to fresh outbreaks of the disease.
The season of the year does not appear to exert any very marked influence upon the development of epidemics, if we base our deductions upon observations made in different countries. In northern countries the disease has prevailed as severely in mid-winter as in summer. The epidemics of London showed a rise during July and August, their furious prevalence in September, and a gradual decline during October and November. In Constantinople the disease has commonly remained dormant during the winter months, and become active as the weather grew hotter. In Egypt, on the contrary, the activity of the outbreaks has developed in winter, increased with the advance of spring, and suddenly abated upon the advent of the summer. Such also has been the case with the three general epidemics in Mesopotamia studied by Tholozan.4 "Their beginning took place in winter, their development during the spring, their decline and their extinction in summer. Their recrudescences obeyed the same laws: after an incubation during the summer season ... revivification took place in winter and in spring." It is added in this writer's account that the exceptional hot weather of summer in that country, and especially that of the shores of the Persian Gulf, has always moderated or directed the course of epidemics of this pest. In Cairo the epidemics have usually ceased upon the recurrence of intense summer heat in June. Dampness, and particularly a thoroughly wet soil, are favorable to the development and spread of the disease. The marshy regions of the Lower Euphrates, the shores of the Caspian and the Black Seas, the valley of the Nile, have been the scenes of repeated visitations. On the other hand, the plague has maintained its foothold in the mountainous districts of Western Arabia, in Yunnan, on the slopes of the Himalayas at a great elevation, and upon a dry, non-alluvial soil even more firmly than in the low and humid plains of Mesopotamia.5
4 Histoire de la Peste Bubonique en Mesopotamie, 2d Mémoire, Paris, 1874.
5 Tholozan, Histoire de la Peste Bubonique en Perse, 1st Mémoire, Paris, 1874.