7 o POPULAR SCIENCE MONTHLY. 



There is no known racial immunity to this disease. It is alike 

 fatal to Mongolians, Africans, and Europeans. It has prevailed 

 in the marshes along the Euphrates and on the Himalayas ; in 

 densely populated cities and in sparsely settled rural districts ; on 

 the sands of Egypt and amid the snows of Norway. 



Climate and season have been studied in order to establish be- 

 tween them and the plague a causal relationship. Epidemics have 

 followed prolonged droughts, and have prevailed during rainy 

 seasons. The wind may blow where it listeth, but the bacillus 

 heedeth it not. The epidemic at Hong Kong in 1894 appeared 

 after a prolonged season of dry weather. Rain was anxiously 

 looked for probably prayed for. It was said, All will be well 

 when the rain comes. At last the rain did come, and with it the 

 disease seemed to be refreshed and the number of deaths was mul- 

 tiplied. The attempt to find in meteorological conditions a cause 

 for our ills is a relic of the superstition of ages when it was be- 

 lieved that disease was sent from heaven to afflict man for his 

 sins, and was due to the anger of the gods. 



Overcrowding is undoubtedly a factor in the distribution of 

 this disease, as it is of all other infectious diseases, simply because 

 it renders transmission of the germ from one to the other more 

 speedy and certain ; but that the disease can be due to overcrowd- 

 ing is, in the present state of our knowledge, an absurdity. 



Poverty and famine are factors in the propagation of the dis- 

 ease. Want of proper food renders the individual more suscep- 

 tible. This has been demonstrated in case of more than one in- 

 fectious disease by experiments upon the lower animals. Priva- 

 tion has always been associated with the most notable outbreaks 

 of the plagues. As stated in the beginning of this paper, famine 

 and disease are twin brothers, inseparable. Where one of them 

 dwells there the other may be found. This is undoubtedly the 

 reason why this disease has always found a home in the Levan- 

 tine. Cantline says : " In the densely packed cities of Asia the 

 poor exist forever on the fringe of destitution, and the least rise 

 in the price of food brings scarcity, so that the term, ' the poor 

 man's plague/ holds good for all time." 



There has been much written concerning the period of incuba- 

 tion of this disease, but necessarily all is indefinite. Because a 

 well man comes in contact with a sick one on a certain day, and 

 manifests the first symptoms of the disease ten days later, does 

 not prove that the period of incubation is ten days. The well man 

 may have carried on his person the bacillus from the sick-room, 

 and any time subsequent thereto it may have been introduced into 

 the body. All that is said about the period of incubation of the 

 infectious disease is based on the old theory long since exploded 

 that the well man breathes in the miasm at the time of his com- 



